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	$182.77	9.140%	$199.4752	$199.48	$199.50	$199.50
Purchase #2	$77.30	4.468%	$80.7538	$80.75	$80.75	$80.80
Purchase #3	$137.91	6.148%	$146.3887	$146.39	$146.40	$146.40
Purchase #4	$193.49	6.262%	$205.6063	$205.61	$205.60	$205.60
Purchase #5	$5.83	4.147%	$6.0718	$6.07	$6.05	$6.10
Purchase #6	$30.69	4.248%	$31.9937	$31.99	$32.00	$32.00
Purchase #7	$84.51	7.614%	$90.9446	$90.94	$90.95	$90.90
7 purchase totals =	$712.50		$761.2341	$761.23	$761.25	$761.30