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	$160.52	7.386%	$172.376	$172.38	$172.40	$172.40
Purchase #2	$29.38	10.821%	$32.5592	$32.56	$32.55	$32.60
Purchase #3	$195.86	12.648%	$220.6324	$220.63	$220.65	$220.60
Purchase #4	$151.65	12.679%	$170.8777	$170.88	$170.90	$170.90
Purchase #5	$240.94	4.648%	$252.1389	$252.14	$252.15	$252.10
Purchase #6	$161.93	6.228%	$172.015	$172.02	$172.00	$172.00
Purchase #7	$91.33	9.234%	$99.7634	$99.76	$99.75	$99.80
7 purchase totals =	$1,031.61		$1,120.3626	$1,120.37	$1,120.40	$1,120.40