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 $209.84   5.803%   $222.017   $222.02   $222.00   $222.00  
  Purchase #2 $76.36   4.319%   $79.658   $79.66   $79.65   $79.70  
  Purchase #3 $93.75   5.254%   $98.6756   $98.68   $98.70   $98.70  
  Purchase #4 $16.96   13.307%   $19.2169   $19.22   $19.20   $19.20  
  Purchase #5 $90.56   13.811%   $103.0672   $103.07   $103.05   $103.10  
  Purchase #6 $204.94   10.376%   $226.2046   $226.20   $226.20   $226.20  
  Purchase #7 $165.29   11.118%   $183.6669   $183.67   $183.65   $183.70  
  7 purchase totals = $857.70       $932.5062   $932.52   $932.45   $932.60