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 $32.55   7.626%   $35.0323   $35.03   $35.05   $35.00  
  Purchase #2 $239.62   6.650%   $255.5547   $255.55   $255.55   $255.60  
  Purchase #3 $149.42   3.732%   $154.9964   $155.00   $155.00   $155.00  
  Purchase #4 $232.33   6.656%   $247.7939   $247.79   $247.80   $247.80  
  Purchase #5 $240.83   9.460%   $263.6125   $263.61   $263.60   $263.60  
  Purchase #6 $49.37   5.707%   $52.1875   $52.19   $52.20   $52.20  
  Purchase #7 $169.35   12.843%   $191.0996   $191.10   $191.10   $191.10  
  7 purchase totals = $1,113.47       $1,200.2769   $1,200.27   $1,200.30   $1,200.30