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 $193.48   8.660%   $210.2354   $210.24   $210.25   $210.20  
  Purchase #2 $67.35   7.267%   $72.2443   $72.24   $72.25   $72.20  
  Purchase #3 $67.28   12.165%   $75.4646   $75.46   $75.45   $75.50  
  Purchase #4 $204.30   6.263%   $217.0953   $217.10   $217.10   $217.10  
  Purchase #5 $227.94   6.149%   $241.956   $241.96   $241.95   $242.00  
  Purchase #6 $52.79   3.385%   $54.5769   $54.58   $54.60   $54.60  
  Purchase #7 $199.29   11.218%   $221.6464   $221.65   $221.65   $221.60  
  7 purchase totals = $1,012.43       $1,093.2189   $1,093.23   $1,093.25   $1,093.20