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	$167.94	13.662%	$190.884	$190.88	$190.90	$190.90
Purchase #2	$194.63	8.319%	$210.8213	$210.82	$210.80	$210.80
Purchase #3	$56.80	4.654%	$59.4435	$59.44	$59.45	$59.40
Purchase #4	$159.83	9.538%	$175.0746	$175.07	$175.05	$175.10
Purchase #5	$97.89	13.307%	$110.9162	$110.92	$110.90	$110.90
Purchase #6	$223.71	9.426%	$244.7969	$244.80	$244.80	$244.80
Purchase #7	$213.63	5.630%	$225.6574	$225.66	$225.65	$225.70
7 purchase totals =	$1,114.43		$1,217.5939	$1,217.59	$1,217.55	$1,217.60