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	$142.43	3.843%	$147.9036	$147.90	$147.90	$147.90
Purchase #2	$149.84	10.600%	$165.723	$165.72	$165.70	$165.70
Purchase #3	$171.83	13.578%	$195.1611	$195.16	$195.15	$195.20
Purchase #4	$63.34	5.739%	$66.9751	$66.98	$67.00	$67.00
Purchase #5	$165.36	4.379%	$172.6011	$172.60	$172.60	$172.60
Purchase #6	$239.63	13.246%	$271.3714	$271.37	$271.35	$271.40
Purchase #7	$136.64	7.488%	$146.8716	$146.87	$146.85	$146.90
7 purchase totals =	$1,069.07		$1,166.6069	$1,166.60	$1,166.55	$1,166.70