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	$183.41	6.406%	$195.1592	$195.16	$195.15	$195.20
Purchase #2	$106.80	9.569%	$117.0197	$117.02	$117.00	$117.00
Purchase #3	$105.56	12.519%	$118.7751	$118.78	$118.80	$118.80
Purchase #4	$153.72	9.683%	$168.6047	$168.60	$168.60	$168.60
Purchase #5	$48.78	3.648%	$50.5595	$50.56	$50.55	$50.60
Purchase #6	$193.26	10.150%	$212.8759	$212.88	$212.90	$212.90
Purchase #7	$89.95	10.620%	$99.5027	$99.50	$99.50	$99.50
7 purchase totals =	$881.48		$962.4968	$962.50	$962.50	$962.60