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	$61.44	7.415%	$65.9958	$66.00	$66.00	$66.00
Purchase #2	$166.83	3.460%	$172.6023	$172.60	$172.60	$172.60
Purchase #3	$239.33	6.355%	$254.5394	$254.54	$254.55	$254.50
Purchase #4	$211.87	6.555%	$225.7581	$225.76	$225.75	$225.80
Purchase #5	$116.62	9.649%	$127.8727	$127.87	$127.85	$127.90
Purchase #6	$182.79	4.233%	$190.5275	$190.53	$190.55	$190.50
Purchase #7	$168.74	7.415%	$181.2521	$181.25	$181.25	$181.30
7 purchase totals =	$1,147.62		$1,218.5479	$1,218.55	$1,218.55	$1,218.60