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 $220.84   10.567%   $244.1762   $244.18   $244.20   $244.20  
  Purchase #2 $87.72   7.606%   $94.392   $94.39   $94.40   $94.40  
  Purchase #3 $39.63   10.209%   $43.6758   $43.68   $43.70   $43.70  
  Purchase #4 $165.78   3.290%   $171.2342   $171.23   $171.25   $171.20  
  Purchase #5 $171.67   13.354%   $194.5948   $194.59   $194.60   $194.60  
  Purchase #6 $98.87   11.469%   $110.2094   $110.21   $110.20   $110.20  
  Purchase #7 $87.25   9.650%   $95.6696   $95.67   $95.65   $95.70  
  7 purchase totals = $871.76       $953.9520   $953.95   $954.00   $954.00