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	$120.56	5.749%	$127.491	$127.49	$127.50	$127.50
Purchase #2	$83.77	3.471%	$86.6777	$86.68	$86.70	$86.70
Purchase #3	$143.76	10.279%	$158.5371	$158.54	$158.55	$158.50
Purchase #4	$188.67	11.454%	$210.2803	$210.28	$210.30	$210.30
Purchase #5	$207.40	10.699%	$229.5897	$229.59	$229.60	$229.60
Purchase #6	$147.87	3.384%	$152.8739	$152.87	$152.85	$152.90
Purchase #7	$178.79	12.146%	$200.5058	$200.51	$200.50	$200.50
7 purchase totals =	$1,070.82		$1,165.9555	$1,165.96	$1,166.00	$1,166.00