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	$190.51	7.668%	$205.1183	$205.12	$205.10	$205.10
Purchase #2	$177.49	6.218%	$188.5263	$188.53	$188.55	$188.50
Purchase #3	$20.30	5.708%	$21.4587	$21.46	$21.45	$21.50
Purchase #4	$142.73	10.177%	$157.2556	$157.26	$157.25	$157.30
Purchase #5	$117.43	8.795%	$127.758	$127.76	$127.75	$127.80
Purchase #6	$166.57	7.550%	$179.146	$179.15	$179.15	$179.10
Purchase #7	$174.48	4.551%	$182.4206	$182.42	$182.40	$182.40
7 purchase totals =	$989.51		$1,061.6835	$1,061.70	$1,061.65	$1,061.70