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 $59.37   4.155%   $61.8368   $61.84   $61.85   $61.80  
  Purchase #2 $134.56   11.464%   $149.986   $149.99   $150.00   $150.00  
  Purchase #3 $143.89   11.333%   $160.1971   $160.20   $160.20   $160.20  
  Purchase #4 $173.36   7.380%   $186.154   $186.15   $186.15   $186.20  
  Purchase #5 $12.49   6.438%   $13.2941   $13.29   $13.30   $13.30  
  Purchase #6 $123.28   9.649%   $135.1753   $135.18   $135.20   $135.20  
  Purchase #7 $149.68   8.415%   $162.2756   $162.28   $162.30   $162.30  
  7 purchase totals = $796.63       $868.9189   $868.93   $869.00   $869.00