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 $67.59   9.523%   $74.0266   $74.03   $74.05   $74.00  
  Purchase #2 $75.50   12.513%   $84.9473   $84.95   $84.95   $84.90  
  Purchase #3 $15.76   5.864%   $16.6842   $16.68   $16.70   $16.70  
  Purchase #4 $235.27   4.120%   $244.9631   $244.96   $244.95   $245.00  
  Purchase #5 $233.95   5.363%   $246.4967   $246.50   $246.50   $246.50  
  Purchase #6 $18.50   12.410%   $20.7959   $20.80   $20.80   $20.80  
  Purchase #7 $158.71   8.310%   $171.8988   $171.90   $171.90   $171.90  
  7 purchase totals = $805.28       $859.8126   $859.82   $859.85   $859.80