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 $87.75   9.533%   $96.1152   $96.12   $96.10   $96.10  
  Purchase #2 $194.32   9.593%   $212.9611   $212.96   $212.95   $213.00  
  Purchase #3 $212.39   11.590%   $237.006   $237.01   $237.00   $237.00  
  Purchase #4 $182.48   9.232%   $199.3266   $199.33   $199.35   $199.30  
  Purchase #5 $5.81   7.398%   $6.2398   $6.24   $6.25   $6.20  
  Purchase #6 $30.80   11.306%   $34.2822   $34.28   $34.30   $34.30  
  Purchase #7 $228.36   7.189%   $244.7768   $244.78   $244.80   $244.80  
  7 purchase totals = $941.91       $1,030.7077   $1,030.72   $1,030.75   $1,030.70