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 $65.27   7.789%   $70.3539   $70.35   $70.35   $70.40  
  Purchase #2 $208.69   12.772%   $235.3439   $235.34   $235.35   $235.30  
  Purchase #3 $164.50   7.376%   $176.6335   $176.63   $176.65   $176.60  
  Purchase #4 $211.32   3.625%   $218.9804   $218.98   $219.00   $219.00  
  Purchase #5 $147.82   3.736%   $153.3426   $153.34   $153.35   $153.30  
  Purchase #6 $138.41   13.583%   $157.2102   $157.21   $157.20   $157.20  
  Purchase #7 $88.96   6.762%   $94.9755   $94.98   $95.00   $95.00  
  7 purchase totals = $1,024.97       $1,106.8400   $1,106.83   $1,106.90   $1,106.80