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 $172.49   13.467%   $195.7192   $195.72   $195.70   $195.70  
  Purchase #2 $205.25   6.623%   $218.8437   $218.84   $218.85   $218.80  
  Purchase #3 $67.77   9.396%   $74.1377   $74.14   $74.15   $74.10  
  Purchase #4 $16.98   9.226%   $18.5466   $18.55   $18.55   $18.50  
  Purchase #5 $221.39   13.761%   $251.8555   $251.86   $251.85   $251.90  
  Purchase #6 $213.73   11.578%   $238.4757   $238.48   $238.50   $238.50  
  Purchase #7 $87.90   3.378%   $90.8693   $90.87   $90.85   $90.90  
  7 purchase totals = $985.51       $1,088.4477   $1,088.46   $1,088.45   $1,088.40