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 $205.31   6.823%   $219.3183   $219.32   $219.30   $219.30  
  Purchase #2 $201.74   13.344%   $228.6602   $228.66   $228.65   $228.70  
  Purchase #3 $199.32   6.347%   $211.9708   $211.97   $211.95   $212.00  
  Purchase #4 $24.92   8.796%   $27.112   $27.11   $27.10   $27.10  
  Purchase #5 $71.87   5.716%   $75.9781   $75.98   $76.00   $76.00  
  Purchase #6 $67.43   6.355%   $71.7152   $71.72   $71.70   $71.70  
  Purchase #7 $225.85   3.383%   $233.4905   $233.49   $233.50   $233.50  
  7 purchase totals = $996.44       $1,068.2451   $1,068.25   $1,068.20   $1,068.30