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 $89.45   7.687%   $96.326   $96.33   $96.35   $96.30  
  Purchase #2 $125.73   7.431%   $135.073   $135.07   $135.05   $135.10  
  Purchase #3 $44.32   12.177%   $49.7168   $49.72   $49.70   $49.70  
  Purchase #4 $240.49   10.465%   $265.6573   $265.66   $265.65   $265.70  
  Purchase #5 $167.86   7.682%   $180.755   $180.76   $180.75   $180.80  
  Purchase #6 $245.51   10.286%   $270.7632   $270.76   $270.75   $270.80  
  Purchase #7 $62.40   4.150%   $64.9896   $64.99   $65.00   $65.00  
  7 purchase totals = $975.76       $1,063.2809   $1,063.29   $1,063.25   $1,063.40