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	$145.57	10.800%	$161.2916	$161.29	$161.30	$161.30
Purchase #2	$183.74	11.653%	$205.1512	$205.15	$205.15	$205.20
Purchase #3	$146.74	13.225%	$166.1464	$166.15	$166.15	$166.10
Purchase #4	$247.69	3.292%	$255.844	$255.84	$255.85	$255.80
Purchase #5	$232.92	7.614%	$250.6545	$250.65	$250.65	$250.70
Purchase #6	$127.35	11.606%	$142.1302	$142.13	$142.15	$142.10
Purchase #7	$117.89	7.803%	$127.089	$127.09	$127.10	$127.10
7 purchase totals =	$1,201.90		$1,308.3069	$1,308.30	$1,308.35	$1,308.30