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 $58.88   6.290%   $62.5836   $62.58   $62.60   $62.60  
  Purchase #2 $159.28   6.437%   $169.5329   $169.53   $169.55   $169.50  
  Purchase #3 $204.34   10.661%   $226.1247   $226.12   $226.10   $226.10  
  Purchase #4 $124.52   4.196%   $129.7449   $129.74   $129.75   $129.70  
  Purchase #5 $180.35   13.677%   $205.0165   $205.02   $205.00   $205.00  
  Purchase #6 $106.35   10.695%   $117.7241   $117.72   $117.70   $117.70  
  Purchase #7 $113.71   8.709%   $123.613   $123.61   $123.60   $123.60  
  7 purchase totals = $947.43       $1,034.3397   $1,034.32   $1,034.30   $1,034.20