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 $59.82   3.557%   $61.9478   $61.95   $61.95   $61.90  
  Purchase #2 $54.99   9.223%   $60.0617   $60.06   $60.05   $60.10  
  Purchase #3 $219.26   3.293%   $226.4802   $226.48   $226.50   $226.50  
  Purchase #4 $81.27   8.221%   $87.9512   $87.95   $87.95   $88.00  
  Purchase #5 $68.47   4.198%   $71.3444   $71.34   $71.35   $71.30  
  Purchase #6 $102.36   4.490%   $106.956   $106.96   $106.95   $107.00  
  Purchase #7 $203.30   6.364%   $216.238   $216.24   $216.25   $216.20  
  7 purchase totals = $789.47       $830.9793   $830.98   $831.00   $831.00