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 $116.31   5.827%   $123.0874   $123.09   $123.10   $123.10  
  Purchase #2 $245.72   8.529%   $266.6775   $266.68   $266.70   $266.70  
  Purchase #3 $32.44   7.761%   $34.9577   $34.96   $34.95   $35.00  
  Purchase #4 $99.84   3.406%   $103.2406   $103.24   $103.25   $103.20  
  Purchase #5 $237.40   6.359%   $252.4963   $252.50   $252.50   $252.50  
  Purchase #6 $202.57   8.145%   $219.0693   $219.07   $219.05   $219.10  
  Purchase #7 $235.49   5.114%   $247.533   $247.53   $247.55   $247.50  
  7 purchase totals = $1,169.77       $1,247.0618   $1,247.07   $1,247.10   $1,247.10