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	$49.83	7.183%	$53.4093	$53.41	$53.40	$53.40
Purchase #2	$130.91	13.171%	$148.1522	$148.15	$148.15	$148.20
Purchase #3	$148.95	8.190%	$161.149	$161.15	$161.15	$161.10
Purchase #4	$31.57	3.282%	$32.6061	$32.61	$32.60	$32.60
Purchase #5	$144.47	7.752%	$155.6693	$155.67	$155.65	$155.70
Purchase #6	$91.64	8.250%	$99.2003	$99.20	$99.20	$99.20
Purchase #7	$122.37	4.175%	$127.4789	$127.48	$127.50	$127.50
7 purchase totals =	$719.74		$777.6651	$777.67	$777.65	$777.70