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	$150.91	11.759%	$168.6555	$168.66	$168.65	$168.70
Purchase #2	$144.96	13.251%	$164.1686	$164.17	$164.15	$164.20
Purchase #3	$22.76	6.578%	$24.2572	$24.26	$24.25	$24.30
Purchase #4	$112.92	13.254%	$127.8864	$127.89	$127.90	$127.90
Purchase #5	$100.70	4.680%	$105.4128	$105.41	$105.40	$105.40
Purchase #6	$188.48	12.179%	$211.435	$211.44	$211.45	$211.40
Purchase #7	$17.30	13.267%	$19.5952	$19.60	$19.60	$19.60
7 purchase totals =	$738.03		$821.4107	$821.43	$821.40	$821.50