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 $219.52   9.804%   $241.0417   $241.04   $241.05   $241.00  
  Purchase #2 $192.56   12.185%   $216.0234   $216.02   $216.00   $216.00  
  Purchase #3 $211.61   8.405%   $229.3958   $229.40   $229.40   $229.40  
  Purchase #4 $192.59   5.362%   $202.9167   $202.92   $202.90   $202.90  
  Purchase #5 $199.38   3.806%   $206.9684   $206.97   $206.95   $207.00  
  Purchase #6 $225.64   9.459%   $246.9833   $246.98   $247.00   $247.00  
  Purchase #7 $131.42   13.728%   $149.4613   $149.46   $149.45   $149.50  
  7 purchase totals = $1,372.72       $1,492.7906   $1,492.79   $1,492.75   $1,492.80