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	$195.46	7.784%	$210.6746	$210.67	$210.65	$210.70
Purchase #2	$112.34	13.487%	$127.4913	$127.49	$127.50	$127.50
Purchase #3	$222.31	6.700%	$237.2048	$237.20	$237.20	$237.20
Purchase #4	$213.92	3.513%	$221.435	$221.44	$221.45	$221.40
Purchase #5	$151.79	4.451%	$158.5462	$158.55	$158.55	$158.50
Purchase #6	$237.41	7.454%	$255.1065	$255.11	$255.10	$255.10
Purchase #7	$12.28	13.355%	$13.92	$13.92	$13.90	$13.90
7 purchase totals =	$1,145.51		$1,224.3784	$1,224.38	$1,224.35	$1,224.30