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 $85.51   11.839%   $95.6335   $95.63   $95.65   $95.60  
  Purchase #2 $124.75   5.274%   $131.3293   $131.33   $131.35   $131.30  
  Purchase #3 $82.62   5.672%   $87.3062   $87.31   $87.30   $87.30  
  Purchase #4 $107.37   11.363%   $119.5705   $119.57   $119.55   $119.60  
  Purchase #5 $106.62   8.758%   $115.9578   $115.96   $115.95   $116.00  
  Purchase #6 $76.35   7.834%   $82.3313   $82.33   $82.35   $82.30  
  Purchase #7 $110.84   10.216%   $122.1634   $122.16   $122.15   $122.20  
  7 purchase totals = $694.06       $754.2920   $754.29   $754.30   $754.30