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 $68.33   6.781%   $72.9635   $72.96   $72.95   $73.00  
  Purchase #2 $201.48   9.619%   $220.8604   $220.86   $220.85   $220.90  
  Purchase #3 $30.60   11.794%   $34.209   $34.21   $34.20   $34.20  
  Purchase #4 $137.86   11.204%   $153.3058   $153.31   $153.30   $153.30  
  Purchase #5 $234.84   8.235%   $254.1791   $254.18   $254.20   $254.20  
  Purchase #6 $67.25   5.261%   $70.788   $70.79   $70.80   $70.80  
  Purchase #7 $181.99   13.571%   $206.6879   $206.69   $206.70   $206.70  
  7 purchase totals = $922.35       $1,012.9937   $1,013.00   $1,013.00   $1,013.10