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 $60.98   11.558%   $68.0281   $68.03   $68.05   $68.00  
  Purchase #2 $195.71   9.410%   $214.1263   $214.13   $214.15   $214.10  
  Purchase #3 $247.51   8.746%   $269.1572   $269.16   $269.15   $269.20  
  Purchase #4 $224.65   8.405%   $243.5318   $243.53   $243.55   $243.50  
  Purchase #5 $84.70   6.183%   $89.937   $89.94   $89.95   $89.90  
  Purchase #6 $192.90   7.178%   $206.7464   $206.75   $206.75   $206.70  
  Purchase #7 $172.68   10.152%   $190.2105   $190.21   $190.20   $190.20  
  7 purchase totals = $1,179.13       $1,281.7373   $1,281.75   $1,281.80   $1,281.60