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 $58.34   7.819%   $62.9016   $62.90   $62.90   $62.90  
  Purchase #2 $218.46   10.404%   $241.1886   $241.19   $241.20   $241.20  
  Purchase #3 $176.81   4.345%   $184.4924   $184.49   $184.50   $184.50  
  Purchase #4 $224.87   9.676%   $246.6284   $246.63   $246.65   $246.60  
  Purchase #5 $56.45   12.180%   $63.3256   $63.33   $63.35   $63.30  
  Purchase #6 $94.60   6.543%   $100.7897   $100.79   $100.80   $100.80  
  Purchase #7 $202.58   7.810%   $218.4015   $218.40   $218.40   $218.40  
  7 purchase totals = $1,032.11       $1,117.7278   $1,117.73   $1,117.80   $1,117.70