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	$56.32	13.548%	$63.9502	$63.95	$63.95	$64.00
Purchase #2	$19.43	10.185%	$21.4089	$21.41	$21.40	$21.40
Purchase #3	$85.56	11.345%	$95.2668	$95.27	$95.25	$95.30
Purchase #4	$243.26	13.428%	$275.925	$275.93	$275.95	$275.90
Purchase #5	$147.38	3.258%	$152.1816	$152.18	$152.20	$152.20
Purchase #6	$97.37	10.393%	$107.4897	$107.49	$107.50	$107.50
Purchase #7	$91.49	13.103%	$103.4779	$103.48	$103.50	$103.50
7 purchase totals =	$740.81		$819.7001	$819.71	$819.75	$819.80