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 $141.25   11.634%   $157.683   $157.68   $157.70   $157.70  
  Purchase #2 $89.52   7.369%   $96.1167   $96.12   $96.10   $96.10  
  Purchase #3 $41.64   11.408%   $46.3903   $46.39   $46.40   $46.40  
  Purchase #4 $231.33   6.118%   $245.4828   $245.48   $245.50   $245.50  
  Purchase #5 $80.39   4.261%   $83.8154   $83.82   $83.80   $83.80  
  Purchase #6 $44.89   5.536%   $47.3751   $47.38   $47.40   $47.40  
  Purchase #7 $188.31   9.582%   $206.3539   $206.35   $206.35   $206.40  
  7 purchase totals = $817.33       $883.2172   $883.22   $883.25   $883.30