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 $54.87   12.719%   $61.8489   $61.85   $61.85   $61.80  
  Purchase #2 $186.45   4.442%   $194.7321   $194.73   $194.75   $194.70  
  Purchase #3 $247.31   11.150%   $274.8851   $274.89   $274.90   $274.90  
  Purchase #4 $11.30   6.720%   $12.0594   $12.06   $12.05   $12.10  
  Purchase #5 $219.93   4.387%   $229.5783   $229.58   $229.60   $229.60  
  Purchase #6 $44.70   7.167%   $47.9036   $47.90   $47.90   $47.90  
  Purchase #7 $211.70   9.284%   $231.3542   $231.35   $231.35   $231.40  
  7 purchase totals = $976.26       $1,052.3616   $1,052.36   $1,052.40   $1,052.40