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 $216.61   9.809%   $237.8573   $237.86   $237.85   $237.90  
  Purchase #2 $60.92   7.813%   $65.6797   $65.68   $65.70   $65.70  
  Purchase #3 $205.58   5.135%   $216.1365   $216.14   $216.15   $216.10  
  Purchase #4 $59.97   13.617%   $68.1361   $68.14   $68.15   $68.10  
  Purchase #5 $202.92   6.226%   $215.5538   $215.55   $215.55   $215.60  
  Purchase #6 $209.91   7.677%   $226.0248   $226.02   $226.00   $226.00  
  Purchase #7 $245.28   11.439%   $273.3376   $273.34   $273.35   $273.30  
  7 purchase totals = $1,201.19       $1,302.7258   $1,302.73   $1,302.75   $1,302.70