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 $186.74   8.261%   $202.1666   $202.17   $202.15   $202.20  
  Purchase #2 $61.53   10.538%   $68.014   $68.01   $68.00   $68.00  
  Purchase #3 $151.91   5.613%   $160.4367   $160.44   $160.45   $160.40  
  Purchase #4 $214.55   8.484%   $232.7524   $232.75   $232.75   $232.80  
  Purchase #5 $100.47   6.166%   $106.665   $106.67   $106.65   $106.70  
  Purchase #6 $166.42   3.844%   $172.8172   $172.82   $172.80   $172.80  
  Purchase #7 $191.49   9.757%   $210.1737   $210.17   $210.15   $210.20  
  7 purchase totals = $1,073.11       $1,153.0256   $1,153.03   $1,152.95   $1,153.10