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 $68.76   10.257%   $75.8127   $75.81   $75.80   $75.80  
  Purchase #2 $218.32   8.411%   $236.6829   $236.68   $236.70   $236.70  
  Purchase #3 $149.52   11.818%   $167.1903   $167.19   $167.20   $167.20  
  Purchase #4 $213.55   4.428%   $223.006   $223.01   $223.00   $223.00  
  Purchase #5 $187.25   8.732%   $203.6007   $203.60   $203.60   $203.60  
  Purchase #6 $234.95   12.412%   $264.112   $264.11   $264.10   $264.10  
  Purchase #7 $75.90   13.344%   $86.0281   $86.03   $86.05   $86.00  
  7 purchase totals = $1,148.25       $1,256.4327   $1,256.43   $1,256.45   $1,256.40