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	$32.34	11.212%	$35.966	$35.97	$35.95	$36.00
Purchase #2	$52.66	3.541%	$54.5247	$54.52	$54.50	$54.50
Purchase #3	$51.31	5.687%	$54.228	$54.23	$54.25	$54.20
Purchase #4	$73.87	11.570%	$82.4168	$82.42	$82.40	$82.40
Purchase #5	$155.65	11.203%	$173.0875	$173.09	$173.10	$173.10
Purchase #6	$157.49	5.550%	$166.2307	$166.23	$166.25	$166.20
Purchase #7	$210.33	8.109%	$227.3857	$227.39	$227.40	$227.40
7 purchase totals =	$733.65		$793.8394	$793.85	$793.85	$793.80