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 $88.33   7.590%   $95.0342   $95.03   $95.05   $95.00  
  Purchase #2 $111.44   6.464%   $118.6435   $118.64   $118.65   $118.60  
  Purchase #3 $250.71   7.457%   $269.4054   $269.41   $269.40   $269.40  
  Purchase #4 $12.59   10.368%   $13.8953   $13.90   $13.90   $13.90  
  Purchase #5 $88.39   13.719%   $100.5162   $100.52   $100.50   $100.50  
  Purchase #6 $46.60   13.782%   $53.0224   $53.02   $53.00   $53.00  
  Purchase #7 $204.96   3.531%   $212.1971   $212.20   $212.20   $212.20  
  7 purchase totals = $803.02       $862.7141   $862.72   $862.70   $862.60