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 $43.39   7.369%   $46.5874   $46.59   $46.60   $46.60  
  Purchase #2 $91.81   11.814%   $102.6564   $102.66   $102.65   $102.70  
  Purchase #3 $67.86   7.850%   $73.187   $73.19   $73.20   $73.20  
  Purchase #4 $187.39   7.253%   $200.9814   $200.98   $201.00   $201.00  
  Purchase #5 $151.35   11.731%   $169.1049   $169.10   $169.10   $169.10  
  Purchase #6 $194.97   4.413%   $203.574   $203.57   $203.55   $203.60  
  Purchase #7 $80.47   6.610%   $85.7891   $85.79   $85.80   $85.80  
  7 purchase totals = $817.24       $881.8802   $881.88   $881.90   $882.00