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 $69.49   7.715%   $74.8512   $74.85   $74.85   $74.90  
  Purchase #2 $208.58   12.824%   $235.3283   $235.33   $235.35   $235.30  
  Purchase #3 $152.60   6.245%   $162.1299   $162.13   $162.15   $162.10  
  Purchase #4 $207.66   12.143%   $232.8762   $232.88   $232.90   $232.90  
  Purchase #5 $119.34   5.560%   $125.9753   $125.98   $126.00   $126.00  
  Purchase #6 $95.67   11.711%   $106.8739   $106.87   $106.85   $106.90  
  Purchase #7 $120.37   9.365%   $131.6427   $131.64   $131.65   $131.60  
  7 purchase totals = $973.71       $1,069.6775   $1,069.68   $1,069.75   $1,069.70