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	$88.88	4.528%	$92.9045	$92.90	$92.90	$92.90
Purchase #2	$60.28	3.664%	$62.4887	$62.49	$62.50	$62.50
Purchase #3	$147.80	6.738%	$157.7588	$157.76	$157.75	$157.80
Purchase #4	$210.92	5.641%	$222.818	$222.82	$222.80	$222.80
Purchase #5	$14.66	3.396%	$15.1579	$15.16	$15.15	$15.20
Purchase #6	$42.63	7.496%	$45.8255	$45.83	$45.85	$45.80
Purchase #7	$85.43	3.872%	$88.7378	$88.74	$88.75	$88.70
7 purchase totals =	$650.60		$685.6912	$685.70	$685.70	$685.70