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	$215.74	3.103%	$222.4344	$222.43	$222.45	$222.40
Purchase #2	$40.75	11.252%	$45.3352	$45.34	$45.35	$45.30
Purchase #3	$35.93	4.338%	$37.4886	$37.49	$37.50	$37.50
Purchase #4	$44.93	3.106%	$46.3255	$46.33	$46.35	$46.30
Purchase #5	$185.30	5.109%	$194.767	$194.77	$194.75	$194.80
Purchase #6	$165.97	4.312%	$173.1266	$173.13	$173.15	$173.10
Purchase #7	$64.76	9.256%	$70.7542	$70.75	$70.75	$70.80
7 purchase totals =	$753.38		$790.2315	$790.24	$790.30	$790.20