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	$80.81	9.191%	$88.2372	$88.24	$88.25	$88.20
Purchase #2	$98.39	10.578%	$108.7977	$108.80	$108.80	$108.80
Purchase #3	$243.79	7.717%	$262.6033	$262.60	$262.60	$262.60
Purchase #4	$92.46	8.334%	$100.1656	$100.17	$100.15	$100.20
Purchase #5	$210.28	4.193%	$219.097	$219.10	$219.10	$219.10
Purchase #6	$111.40	5.243%	$117.2407	$117.24	$117.25	$117.20
Purchase #7	$224.90	13.713%	$255.7405	$255.74	$255.75	$255.70
7 purchase totals =	$1,062.03		$1,151.8820	$1,151.89	$1,151.90	$1,151.80