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 $60.59   10.585%   $67.0035   $67.00   $67.00   $67.00  
  Purchase #2 $97.57   8.453%   $105.8176   $105.82   $105.80   $105.80  
  Purchase #3 $243.69   11.779%   $272.3942   $272.39   $272.40   $272.40  
  Purchase #4 $215.98   12.538%   $243.0596   $243.06   $243.05   $243.10  
  Purchase #5 $201.43   12.629%   $226.8686   $226.87   $226.85   $226.90  
  Purchase #6 $239.90   13.334%   $271.8883   $271.89   $271.90   $271.90  
  Purchase #7 $219.68   11.626%   $245.22   $245.22   $245.20   $245.20  
  7 purchase totals = $1,278.84       $1,432.2518   $1,432.25   $1,432.20   $1,432.30