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	$158.91	5.171%	$167.1272	$167.13	$167.15	$167.10
Purchase #2	$126.77	12.814%	$143.0143	$143.01	$143.00	$143.00
Purchase #3	$19.52	6.785%	$20.8444	$20.84	$20.85	$20.80
Purchase #4	$72.73	8.196%	$78.691	$78.69	$78.70	$78.70
Purchase #5	$23.31	4.772%	$24.4224	$24.42	$24.40	$24.40
Purchase #6	$82.72	10.313%	$91.2509	$91.25	$91.25	$91.30
Purchase #7	$115.49	6.433%	$122.9195	$122.92	$122.90	$122.90
7 purchase totals =	$599.45		$648.2697	$648.26	$648.25	$648.20