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	$245.86	6.571%	$262.0155	$262.02	$262.00	$262.00
Purchase #2	$86.90	9.768%	$95.3884	$95.39	$95.40	$95.40
Purchase #3	$18.71	6.308%	$19.8902	$19.89	$19.90	$19.90
Purchase #4	$95.48	8.152%	$103.2635	$103.26	$103.25	$103.30
Purchase #5	$20.63	7.211%	$22.1176	$22.12	$22.10	$22.10
Purchase #6	$32.35	5.436%	$34.1085	$34.11	$34.10	$34.10
Purchase #7	$121.25	5.370%	$127.7611	$127.76	$127.75	$127.80
7 purchase totals =	$621.18		$664.5448	$664.55	$664.50	$664.60