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 $225.52   4.347%   $235.3234   $235.32   $235.30   $235.30  
  Purchase #2 $246.85   11.660%   $275.6327   $275.63   $275.65   $275.60  
  Purchase #3 $54.72   8.827%   $59.5501   $59.55   $59.55   $59.60  
  Purchase #4 $110.42   7.750%   $118.9776   $118.98   $119.00   $119.00  
  Purchase #5 $112.42   7.453%   $120.7987   $120.80   $120.80   $120.80  
  Purchase #6 $154.91   8.116%   $167.4825   $167.48   $167.50   $167.50  
  Purchase #7 $174.29   7.798%   $187.8811   $187.88   $187.90   $187.90  
  7 purchase totals = $1,079.13       $1,165.6461   $1,165.64   $1,165.70   $1,165.70