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 $87.71   8.131%   $94.8417   $94.84   $94.85   $94.80  
  Purchase #2 $169.53   4.129%   $176.5299   $176.53   $176.55   $176.50  
  Purchase #3 $64.71   13.133%   $73.2084   $73.21   $73.20   $73.20  
  Purchase #4 $168.59   9.653%   $184.864   $184.86   $184.85   $184.90  
  Purchase #5 $171.79   8.767%   $186.8508   $186.85   $186.85   $186.90  
  Purchase #6 $65.45   8.360%   $70.9216   $70.92   $70.90   $70.90  
  Purchase #7 $209.33   8.675%   $227.4894   $227.49   $227.50   $227.50  
  7 purchase totals = $937.11       $1,014.7058   $1,014.70   $1,014.70   $1,014.70