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 $244.56   7.141%   $262.024   $262.02   $262.00   $262.00  
  Purchase #2 $153.35   9.455%   $167.8492   $167.85   $167.85   $167.80  
  Purchase #3 $52.99   13.449%   $60.1166   $60.12   $60.10   $60.10  
  Purchase #4 $127.53   7.240%   $136.7632   $136.76   $136.75   $136.80  
  Purchase #5 $189.29   11.332%   $210.7403   $210.74   $210.75   $210.70  
  Purchase #6 $119.85   13.332%   $135.8284   $135.83   $135.85   $135.80  
  Purchase #7 $107.31   11.196%   $119.3244   $119.32   $119.30   $119.30  
  7 purchase totals = $994.88       $1,092.6461   $1,092.64   $1,092.60   $1,092.50