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 $62.54   10.791%   $69.2887   $69.29   $69.30   $69.30  
  Purchase #2 $220.86   10.561%   $244.185   $244.19   $244.20   $244.20  
  Purchase #3 $32.29   7.619%   $34.7502   $34.75   $34.75   $34.80  
  Purchase #4 $179.74   13.830%   $204.598   $204.60   $204.60   $204.60  
  Purchase #5 $61.46   9.642%   $67.386   $67.39   $67.40   $67.40  
  Purchase #6 $123.47   9.520%   $135.2243   $135.22   $135.20   $135.20  
  Purchase #7 $233.67   10.454%   $258.0979   $258.10   $258.10   $258.10  
  7 purchase totals = $914.03       $1,013.5301   $1,013.54   $1,013.55   $1,013.60