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	$164.33	5.162%	$172.8127	$172.81	$172.80	$172.80
Purchase #2	$95.51	13.211%	$108.1278	$108.13	$108.15	$108.10
Purchase #3	$23.39	3.383%	$24.1813	$24.18	$24.20	$24.20
Purchase #4	$82.64	6.869%	$88.3165	$88.32	$88.30	$88.30
Purchase #5	$38.89	11.459%	$43.3464	$43.35	$43.35	$43.30
Purchase #6	$131.97	13.310%	$149.5352	$149.54	$149.55	$149.50
Purchase #7	$208.80	11.783%	$233.4029	$233.40	$233.40	$233.40
7 purchase totals =	$745.53		$819.7228	$819.73	$819.75	$819.60