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 $243.53   9.756%   $267.2888   $267.29   $267.30   $267.30  
  Purchase #2 $245.35   3.502%   $253.9422   $253.94   $253.95   $253.90  
  Purchase #3 $14.35   13.416%   $16.2752   $16.28   $16.30   $16.30  
  Purchase #4 $86.80   8.279%   $93.9862   $93.99   $94.00   $94.00  
  Purchase #5 $220.30   11.554%   $245.7535   $245.75   $245.75   $245.80  
  Purchase #6 $210.88   3.799%   $218.8913   $218.89   $218.90   $218.90  
  Purchase #7 $66.77   7.749%   $71.944   $71.94   $71.95   $71.90  
  7 purchase totals = $1,087.98       $1,168.0812   $1,168.08   $1,168.15   $1,168.10