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 $186.97   7.506%   $201.004   $201.00   $201.00   $201.00  
  Purchase #2 $165.80   11.386%   $184.678   $184.68   $184.70   $184.70  
  Purchase #3 $117.45   4.413%   $122.6331   $122.63   $122.65   $122.60  
  Purchase #4 $159.27   6.716%   $169.9666   $169.97   $169.95   $170.00  
  Purchase #5 $59.34   7.727%   $63.9252   $63.93   $63.95   $63.90  
  Purchase #6 $245.44   6.145%   $260.5223   $260.52   $260.50   $260.50  
  Purchase #7 $184.61   7.172%   $197.8502   $197.85   $197.85   $197.90  
  7 purchase totals = $1,118.88       $1,200.5794   $1,200.58   $1,200.60   $1,200.60