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 $69.69   7.533%   $74.9397   $74.94   $74.95   $74.90  
  Purchase #2 $142.98   13.673%   $162.5297   $162.53   $162.55   $162.50  
  Purchase #3 $79.26   3.732%   $82.218   $82.22   $82.20   $82.20  
  Purchase #4 $229.73   7.432%   $246.8035   $246.80   $246.80   $246.80  
  Purchase #5 $189.90   4.734%   $198.8899   $198.89   $198.90   $198.90  
  Purchase #6 $203.68   7.612%   $219.1841   $219.18   $219.20   $219.20  
  Purchase #7 $70.99   11.276%   $78.9948   $78.99   $79.00   $79.00  
  7 purchase totals = $986.23       $1,063.5597   $1,063.55   $1,063.60   $1,063.50