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	$99.94	11.682%	$111.615	$111.62	$111.60	$111.60
Purchase #2	$20.89	7.387%	$22.4331	$22.43	$22.45	$22.40
Purchase #3	$103.78	7.131%	$111.1806	$111.18	$111.20	$111.20
Purchase #4	$146.72	11.205%	$163.16	$163.16	$163.15	$163.20
Purchase #5	$100.80	6.542%	$107.3943	$107.39	$107.40	$107.40
Purchase #6	$31.59	12.871%	$35.6559	$35.66	$35.65	$35.70
Purchase #7	$174.55	4.802%	$182.9319	$182.93	$182.95	$182.90
7 purchase totals =	$678.27		$734.3708	$734.37	$734.40	$734.40