Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $176.46   13.303%   $199.9345   $199.93   $199.95   $199.90  
  Purchase #2 $211.29   7.242%   $226.5916   $226.59   $226.60   $226.60  
  Purchase #3 $231.39   4.277%   $241.2866   $241.29   $241.30   $241.30  
  Purchase #4 $212.94   11.313%   $237.0299   $237.03   $237.05   $237.00  
  Purchase #5 $205.31   12.168%   $230.2921   $230.29   $230.30   $230.30  
  Purchase #6 $158.79   5.325%   $167.2456   $167.25   $167.25   $167.20  
  Purchase #7 $176.50   8.864%   $192.145   $192.15   $192.15   $192.10  
  7 purchase totals = $1,372.68       $1,494.5253   $1,494.53   $1,494.60   $1,494.40