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 $69.41   5.456%   $73.197   $73.20   $73.20   $73.20  
  Purchase #2 $27.60   5.478%   $29.1119   $29.11   $29.10   $29.10  
  Purchase #3 $193.88   12.523%   $218.1596   $218.16   $218.15   $218.20  
  Purchase #4 $204.91   13.278%   $232.1179   $232.12   $232.10   $232.10  
  Purchase #5 $55.68   11.663%   $62.174   $62.17   $62.15   $62.20  
  Purchase #6 $147.83   6.290%   $157.1285   $157.13   $157.15   $157.10  
  Purchase #7 $213.89   12.601%   $240.8423   $240.84   $240.85   $240.80  
  7 purchase totals = $913.20       $1,012.7312   $1,012.73   $1,012.70   $1,012.70