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 $177.65   10.273%   $195.9   $195.90   $195.90   $195.90  
  Purchase #2 $44.76   4.752%   $46.887   $46.89   $46.90   $46.90  
  Purchase #3 $209.25   9.161%   $228.4194   $228.42   $228.40   $228.40  
  Purchase #4 $152.84   3.334%   $157.9357   $157.94   $157.95   $157.90  
  Purchase #5 $197.86   7.872%   $213.4355   $213.44   $213.45   $213.40  
  Purchase #6 $181.44   10.634%   $200.7343   $200.73   $200.75   $200.70  
  Purchase #7 $160.64   12.673%   $180.9979   $181.00   $181.00   $181.00  
  7 purchase totals = $1,124.44       $1,224.3098   $1,224.32   $1,224.35   $1,224.20