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 $197.51   7.630%   $212.58   $212.58   $212.60   $212.60  
  Purchase #2 $166.39   9.564%   $182.3035   $182.30   $182.30   $182.30  
  Purchase #3 $16.26   12.774%   $18.3371   $18.34   $18.35   $18.30  
  Purchase #4 $170.70   13.275%   $193.3604   $193.36   $193.35   $193.40  
  Purchase #5 $125.87   7.774%   $135.6551   $135.66   $135.65   $135.70  
  Purchase #6 $135.49   12.419%   $152.3165   $152.32   $152.30   $152.30  
  Purchase #7 $186.43   7.639%   $200.6714   $200.67   $200.65   $200.70  
  7 purchase totals = $998.65       $1,095.2240   $1,095.23   $1,095.20   $1,095.30