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 $187.26   7.522%   $201.3457   $201.35   $201.35   $201.30  
  Purchase #2 $33.46   3.599%   $34.6642   $34.66   $34.65   $34.70  
  Purchase #3 $60.68   3.242%   $62.6472   $62.65   $62.65   $62.60  
  Purchase #4 $101.90   10.237%   $112.3315   $112.33   $112.35   $112.30  
  Purchase #5 $149.66   3.598%   $155.0448   $155.04   $155.05   $155.00  
  Purchase #6 $67.95   9.654%   $74.5099   $74.51   $74.50   $74.50  
  Purchase #7 $113.33   13.580%   $128.7202   $128.72   $128.70   $128.70  
  7 purchase totals = $714.24       $769.2635   $769.26   $769.25   $769.10