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	$9.94	8.171%	$10.7522	$10.75	$10.75	$10.80
Purchase #2	$99.42	13.824%	$113.1638	$113.16	$113.15	$113.20
Purchase #3	$200.85	4.597%	$210.0831	$210.08	$210.10	$210.10
Purchase #4	$128.61	13.121%	$145.4849	$145.48	$145.50	$145.50
Purchase #5	$118.85	7.118%	$127.3097	$127.31	$127.30	$127.30
Purchase #6	$65.50	11.800%	$73.229	$73.23	$73.25	$73.20
Purchase #7	$112.56	4.533%	$117.6623	$117.66	$117.65	$117.70
7 purchase totals =	$735.73		$797.6850	$797.67	$797.70	$797.80