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	$143.88	4.308%	$150.0784	$150.08	$150.10	$150.10
Purchase #2	$205.85	6.748%	$219.7408	$219.74	$219.75	$219.70
Purchase #3	$247.61	11.168%	$275.2631	$275.26	$275.25	$275.30
Purchase #4	$141.40	9.629%	$155.0154	$155.02	$155.00	$155.00
Purchase #5	$32.82	8.149%	$35.4945	$35.49	$35.50	$35.50
Purchase #6	$75.91	10.241%	$83.6839	$83.68	$83.70	$83.70
Purchase #7	$174.66	9.841%	$191.8483	$191.85	$191.85	$191.80
7 purchase totals =	$1,022.13		$1,111.1244	$1,111.12	$1,111.15	$1,111.10