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 $147.43   9.781%   $161.8501   $161.85   $161.85   $161.90  
  Purchase #2 $103.81   3.580%   $107.5264   $107.53   $107.55   $107.50  
  Purchase #3 $113.39   5.166%   $119.2477   $119.25   $119.25   $119.20  
  Purchase #4 $190.81   5.333%   $200.9859   $200.99   $201.00   $201.00  
  Purchase #5 $48.78   6.228%   $51.818   $51.82   $51.80   $51.80  
  Purchase #6 $194.79   13.654%   $221.3866   $221.39   $221.40   $221.40  
  Purchase #7 $175.36   12.543%   $197.3554   $197.36   $197.35   $197.40  
  7 purchase totals = $974.37       $1,060.1701   $1,060.19   $1,060.20   $1,060.20