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 $204.86   5.209%   $215.5312   $215.53   $215.55   $215.50  
  Purchase #2 $244.30   10.454%   $269.8391   $269.84   $269.85   $269.80  
  Purchase #3 $102.64   4.836%   $107.6037   $107.60   $107.60   $107.60  
  Purchase #4 $172.30   7.236%   $184.7676   $184.77   $184.75   $184.80  
  Purchase #5 $232.63   6.214%   $247.0856   $247.09   $247.10   $247.10  
  Purchase #6 $208.39   5.120%   $219.0596   $219.06   $219.05   $219.10  
  Purchase #7 $223.61   8.863%   $243.4286   $243.43   $243.45   $243.40  
  7 purchase totals = $1,388.73       $1,487.3154   $1,487.32   $1,487.35   $1,487.30