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 $199.58   5.866%   $211.2874   $211.29   $211.30   $211.30  
  Purchase #2 $52.65   7.453%   $56.574   $56.57   $56.55   $56.60  
  Purchase #3 $227.51   6.519%   $242.3414   $242.34   $242.35   $242.30  
  Purchase #4 $236.70   3.205%   $244.2862   $244.29   $244.30   $244.30  
  Purchase #5 $127.80   4.740%   $133.8577   $133.86   $133.85   $133.90  
  Purchase #6 $149.45   9.361%   $163.44   $163.44   $163.45   $163.40  
  Purchase #7 $134.42   7.597%   $144.6319   $144.63   $144.65   $144.60  
  7 purchase totals = $1,128.11       $1,196.4186   $1,196.42   $1,196.45   $1,196.40