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	$212.42	9.324%	$232.226	$232.23	$232.25	$232.20
Purchase #2	$81.81	9.543%	$89.6171	$89.62	$89.60	$89.60
Purchase #3	$249.49	13.661%	$283.5728	$283.57	$283.55	$283.60
Purchase #4	$90.25	8.466%	$97.8906	$97.89	$97.90	$97.90
Purchase #5	$175.27	11.870%	$196.0745	$196.07	$196.05	$196.10
Purchase #6	$152.41	6.484%	$162.2923	$162.29	$162.30	$162.30
Purchase #7	$47.57	5.818%	$50.3376	$50.34	$50.35	$50.30
7 purchase totals =	$1,009.22		$1,112.0109	$1,112.01	$1,112.00	$1,112.00