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 $187.32   8.648%   $203.5194   $203.52   $203.50   $203.50  
  Purchase #2 $168.70   6.384%   $179.4698   $179.47   $179.45   $179.50  
  Purchase #3 $87.74   8.240%   $94.9698   $94.97   $94.95   $95.00  
  Purchase #4 $245.61   5.750%   $259.7326   $259.73   $259.75   $259.70  
  Purchase #5 $207.29   5.726%   $219.1594   $219.16   $219.15   $219.20  
  Purchase #6 $39.43   7.817%   $42.5122   $42.51   $42.50   $42.50  
  Purchase #7 $143.43   7.498%   $154.1844   $154.18   $154.20   $154.20  
  7 purchase totals = $1,079.52       $1,153.5476   $1,153.54   $1,153.50   $1,153.60