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 $212.48   13.698%   $241.5855   $241.59   $241.60   $241.60  
  Purchase #2 $50.52   4.365%   $52.7252   $52.73   $52.75   $52.70  
  Purchase #3 $211.78   4.417%   $221.1343   $221.13   $221.15   $221.10  
  Purchase #4 $125.50   10.562%   $138.7553   $138.76   $138.75   $138.80  
  Purchase #5 $44.94   7.254%   $48.1999   $48.20   $48.20   $48.20  
  Purchase #6 $177.42   7.707%   $191.0938   $191.09   $191.10   $191.10  
  Purchase #7 $188.84   12.578%   $212.5923   $212.59   $212.60   $212.60  
  7 purchase totals = $1,011.48       $1,106.0863   $1,106.09   $1,106.15   $1,106.10