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 $70.46   7.607%   $75.8199   $75.82   $75.80   $75.80  
  Purchase #2 $217.28   9.129%   $237.1155   $237.12   $237.10   $237.10  
  Purchase #3 $211.29   3.623%   $218.945   $218.95   $218.95   $218.90  
  Purchase #4 $238.79   12.276%   $268.1039   $268.10   $268.10   $268.10  
  Purchase #5 $55.82   11.353%   $62.1572   $62.16   $62.15   $62.20  
  Purchase #6 $216.93   10.697%   $240.135   $240.14   $240.15   $240.10  
  Purchase #7 $91.77   3.678%   $95.1453   $95.15   $95.15   $95.10  
  7 purchase totals = $1,102.34       $1,197.4218   $1,197.44   $1,197.40   $1,197.30