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 $212.57   7.699%   $228.9358   $228.94   $228.95   $228.90  
  Purchase #2 $237.92   9.791%   $261.2147   $261.21   $261.20   $261.20  
  Purchase #3 $38.62   7.303%   $41.4404   $41.44   $41.45   $41.40  
  Purchase #4 $198.39   7.334%   $212.9399   $212.94   $212.95   $212.90  
  Purchase #5 $219.98   9.761%   $241.4522   $241.45   $241.45   $241.50  
  Purchase #6 $228.81   3.837%   $237.5894   $237.59   $237.60   $237.60  
  Purchase #7 $217.39   12.373%   $244.2877   $244.29   $244.30   $244.30  
  7 purchase totals = $1,353.68       $1,467.8601   $1,467.86   $1,467.90   $1,467.80