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 $183.80   7.510%   $197.6034   $197.60   $197.60   $197.60  
  Purchase #2 $209.68   3.474%   $216.9643   $216.96   $216.95   $217.00  
  Purchase #3 $53.42   6.123%   $56.6909   $56.69   $56.70   $56.70  
  Purchase #4 $195.89   8.542%   $212.6229   $212.62   $212.60   $212.60  
  Purchase #5 $64.98   3.142%   $67.0217   $67.02   $67.00   $67.00  
  Purchase #6 $102.65   6.483%   $109.3048   $109.30   $109.30   $109.30  
  Purchase #7 $224.93   3.128%   $231.9658   $231.97   $231.95   $232.00  
  7 purchase totals = $1,035.35       $1,092.1738   $1,092.16   $1,092.10   $1,092.20