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	$147.90	8.454%	$160.4035	$160.40	$160.40	$160.40
Purchase #2	$100.92	4.346%	$105.306	$105.31	$105.30	$105.30
Purchase #3	$134.78	12.831%	$152.0736	$152.07	$152.05	$152.10
Purchase #4	$49.52	8.422%	$53.6906	$53.69	$53.70	$53.70
Purchase #5	$156.63	5.435%	$165.1428	$165.14	$165.15	$165.10
Purchase #6	$25.69	7.857%	$27.7085	$27.71	$27.70	$27.70
Purchase #7	$177.86	12.622%	$200.3095	$200.31	$200.30	$200.30
7 purchase totals =	$793.30		$864.6345	$864.63	$864.60	$864.60