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	$146.61	8.204%	$158.6379	$158.64	$158.65	$158.60
Purchase #2	$103.58	5.283%	$109.0521	$109.05	$109.05	$109.10
Purchase #3	$164.27	6.390%	$174.7669	$174.77	$174.75	$174.80
Purchase #4	$42.76	6.318%	$45.4616	$45.46	$45.45	$45.50
Purchase #5	$148.96	11.453%	$166.0204	$166.02	$166.00	$166.00
Purchase #6	$105.53	13.251%	$119.5138	$119.51	$119.50	$119.50
Purchase #7	$107.57	4.650%	$112.572	$112.57	$112.55	$112.60
7 purchase totals =	$819.28		$886.0247	$886.02	$885.95	$886.10