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	$17.58	3.759%	$18.2408	$18.24	$18.25	$18.20
Purchase #2	$105.72	4.621%	$110.6053	$110.61	$110.60	$110.60
Purchase #3	$45.46	10.569%	$50.2647	$50.26	$50.25	$50.30
Purchase #4	$159.74	7.743%	$172.1087	$172.11	$172.10	$172.10
Purchase #5	$88.40	3.305%	$91.3216	$91.32	$91.30	$91.30
Purchase #6	$95.27	10.637%	$105.4039	$105.40	$105.40	$105.40
Purchase #7	$23.27	8.425%	$25.2305	$25.23	$25.25	$25.20
7 purchase totals =	$535.44		$573.1755	$573.17	$573.15	$573.10