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 $169.43   7.441%   $182.0373   $182.04   $182.05   $182.00  
  Purchase #2 $173.98   11.485%   $193.9616   $193.96   $193.95   $194.00  
  Purchase #3 $82.69   3.179%   $85.3187   $85.32   $85.30   $85.30  
  Purchase #4 $130.56   5.704%   $138.0071   $138.01   $138.00   $138.00  
  Purchase #5 $200.69   7.462%   $215.6655   $215.67   $215.65   $215.70  
  Purchase #6 $180.68   11.431%   $201.3335   $201.33   $201.35   $201.30  
  Purchase #7 $36.52   12.196%   $40.974   $40.97   $40.95   $41.00  
  7 purchase totals = $974.55       $1,057.2977   $1,057.30   $1,057.25   $1,057.30