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	$172.41	7.217%	$184.8528	$184.85	$184.85	$184.90
Purchase #2	$82.65	6.517%	$88.0363	$88.04	$88.05	$88.00
Purchase #3	$107.77	3.654%	$111.7079	$111.71	$111.70	$111.70
Purchase #4	$100.90	7.841%	$108.8116	$108.81	$108.80	$108.80
Purchase #5	$132.92	11.204%	$147.8124	$147.81	$147.80	$147.80
Purchase #6	$182.77	12.224%	$205.1118	$205.11	$205.10	$205.10
Purchase #7	$99.73	9.456%	$109.1605	$109.16	$109.15	$109.20
7 purchase totals =	$879.15		$955.4933	$955.49	$955.45	$955.50