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	$121.99	4.231%	$127.1514	$127.15	$127.15	$127.20
Purchase #2	$199.91	7.595%	$215.0932	$215.09	$215.10	$215.10
Purchase #3	$211.66	5.545%	$223.3965	$223.40	$223.40	$223.40
Purchase #4	$42.83	6.803%	$45.7437	$45.74	$45.75	$45.70
Purchase #5	$74.45	10.614%	$82.3521	$82.35	$82.35	$82.40
Purchase #6	$35.77	3.517%	$37.028	$37.03	$37.05	$37.00
Purchase #7	$40.91	11.848%	$45.757	$45.76	$45.75	$45.80
7 purchase totals =	$727.52		$776.5219	$776.52	$776.55	$776.60