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 $214.41   10.698%   $237.3476   $237.35   $237.35   $237.30  
  Purchase #2 $73.72   5.529%   $77.796   $77.80   $77.80   $77.80  
  Purchase #3 $153.95   13.787%   $175.1751   $175.18   $175.20   $175.20  
  Purchase #4 $26.49   10.638%   $29.308   $29.31   $29.30   $29.30  
  Purchase #5 $241.47   6.368%   $256.8468   $256.85   $256.85   $256.80  
  Purchase #6 $148.52   13.841%   $169.0767   $169.08   $169.10   $169.10  
  Purchase #7 $69.83   10.516%   $77.1733   $77.17   $77.15   $77.20  
  7 purchase totals = $928.39       $1,022.7235   $1,022.74   $1,022.75   $1,022.70