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 $174.32   11.315%   $194.0443   $194.04   $194.05   $194.00  
  Purchase #2 $52.37   6.356%   $55.6986   $55.70   $55.70   $55.70  
  Purchase #3 $137.66   5.496%   $145.2258   $145.23   $145.25   $145.20  
  Purchase #4 $87.75   11.301%   $97.6666   $97.67   $97.65   $97.70  
  Purchase #5 $184.44   6.756%   $196.9008   $196.90   $196.90   $196.90  
  Purchase #6 $167.96   5.677%   $177.4951   $177.50   $177.50   $177.50  
  Purchase #7 $177.82   12.449%   $199.9568   $199.96   $199.95   $200.00  
  7 purchase totals = $982.32       $1,066.9880   $1,067.00   $1,067.00   $1,067.00