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 $191.84   11.848%   $214.5692   $214.57   $214.55   $214.60  
  Purchase #2 $136.97   13.553%   $155.5335   $155.53   $155.55   $155.50  
  Purchase #3 $83.58   13.243%   $94.6485   $94.65   $94.65   $94.60  
  Purchase #4 $101.91   4.519%   $106.5153   $106.52   $106.50   $106.50  
  Purchase #5 $214.55   11.311%   $238.8178   $238.82   $238.80   $238.80  
  Purchase #6 $195.29   10.162%   $215.1354   $215.14   $215.15   $215.10  
  Purchase #7 $90.53   3.872%   $94.0353   $94.04   $94.05   $94.00  
  7 purchase totals = $1,014.67       $1,119.2550   $1,119.27   $1,119.25   $1,119.10