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 $137.45   8.773%   $149.5085   $149.51   $149.50   $149.50  
  Purchase #2 $141.27   7.105%   $151.3072   $151.31   $151.30   $151.30  
  Purchase #3 $73.50   10.251%   $81.0345   $81.03   $81.05   $81.00  
  Purchase #4 $91.29   4.518%   $95.4145   $95.41   $95.40   $95.40  
  Purchase #5 $145.86   10.214%   $160.7581   $160.76   $160.75   $160.80  
  Purchase #6 $187.91   10.543%   $207.7214   $207.72   $207.70   $207.70  
  Purchase #7 $186.50   11.156%   $207.3059   $207.31   $207.30   $207.30  
  7 purchase totals = $963.78       $1,053.0501   $1,053.05   $1,053.00   $1,053.00