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 $53.85   5.251%   $56.6777   $56.68   $56.70   $56.70  
  Purchase #2 $92.27   9.784%   $101.2977   $101.30   $101.30   $101.30  
  Purchase #3 $168.75   7.826%   $181.9564   $181.96   $181.95   $182.00  
  Purchase #4 $132.62   13.219%   $150.151   $150.15   $150.15   $150.20  
  Purchase #5 $227.94   3.216%   $235.2706   $235.27   $235.25   $235.30  
  Purchase #6 $228.78   6.605%   $243.8909   $243.89   $243.90   $243.90  
  Purchase #7 $129.80   4.623%   $135.8007   $135.80   $135.80   $135.80  
  7 purchase totals = $1,034.01       $1,105.0450   $1,105.05   $1,105.05   $1,105.20