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	$160.46	9.249%	$175.3009	$175.30	$175.30	$175.30
Purchase #2	$132.93	3.437%	$137.4988	$137.50	$137.50	$137.50
Purchase #3	$42.36	7.229%	$45.4222	$45.42	$45.40	$45.40
Purchase #4	$191.53	4.852%	$200.823	$200.82	$200.80	$200.80
Purchase #5	$163.33	5.603%	$172.4814	$172.48	$172.50	$172.50
Purchase #6	$47.50	3.800%	$49.305	$49.31	$49.30	$49.30
Purchase #7	$162.42	13.711%	$184.6894	$184.69	$184.70	$184.70
7 purchase totals =	$900.53		$965.5207	$965.52	$965.50	$965.50