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 $84.60   13.590%   $96.0971   $96.10   $96.10   $96.10  
  Purchase #2 $71.53   5.373%   $75.3733   $75.37   $75.35   $75.40  
  Purchase #3 $71.81   4.222%   $74.8418   $74.84   $74.85   $74.80  
  Purchase #4 $35.29   4.382%   $36.8364   $36.84   $36.85   $36.80  
  Purchase #5 $155.38   10.675%   $171.9668   $171.97   $171.95   $172.00  
  Purchase #6 $19.92   13.216%   $22.5526   $22.55   $22.55   $22.60  
  Purchase #7 $219.65   4.720%   $230.0175   $230.02   $230.00   $230.00  
  7 purchase totals = $658.18       $707.6855   $707.69   $707.65   $707.70