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 $88.37   8.332%   $95.733   $95.73   $95.75   $95.70  
  Purchase #2 $96.31   4.553%   $100.695   $100.70   $100.70   $100.70  
  Purchase #3 $205.99   3.557%   $213.3171   $213.32   $213.30   $213.30  
  Purchase #4 $171.53   10.251%   $189.1135   $189.11   $189.10   $189.10  
  Purchase #5 $232.38   8.834%   $252.9084   $252.91   $252.90   $252.90  
  Purchase #6 $124.44   11.625%   $138.9062   $138.91   $138.90   $138.90  
  Purchase #7 $47.51   13.301%   $53.8293   $53.83   $53.85   $53.80  
  7 purchase totals = $966.53       $1,044.5025   $1,044.51   $1,044.50   $1,044.40