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	$186.32	7.466%	$200.2307	$200.23	$200.25	$200.20
Purchase #2	$77.51	11.485%	$86.412	$86.41	$86.40	$86.40
Purchase #3	$127.44	5.673%	$134.6697	$134.67	$134.65	$134.70
Purchase #4	$195.95	13.614%	$222.6266	$222.63	$222.65	$222.60
Purchase #5	$222.30	4.550%	$232.4147	$232.41	$232.40	$232.40
Purchase #6	$199.30	7.823%	$214.8912	$214.89	$214.90	$214.90
Purchase #7	$61.68	6.832%	$65.894	$65.89	$65.90	$65.90
7 purchase totals =	$1,070.50		$1,157.1389	$1,157.13	$1,157.15	$1,157.10