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	$185.28	5.170%	$194.859	$194.86	$194.85	$194.90
Purchase #2	$125.47	9.194%	$137.0057	$137.01	$137.00	$137.00
Purchase #3	$111.37	6.559%	$118.6748	$118.67	$118.65	$118.70
Purchase #4	$67.52	7.468%	$72.5624	$72.56	$72.55	$72.60
Purchase #5	$86.52	12.153%	$97.0348	$97.03	$97.05	$97.00
Purchase #6	$123.35	6.823%	$131.7662	$131.77	$131.75	$131.80
Purchase #7	$29.84	11.343%	$33.2248	$33.22	$33.20	$33.20
7 purchase totals =	$729.35		$785.1277	$785.12	$785.05	$785.20