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	$159.71	8.728%	$173.6495	$173.65	$173.65	$173.60
Purchase #2	$229.33	6.431%	$244.0782	$244.08	$244.10	$244.10
Purchase #3	$198.31	5.166%	$208.5547	$208.55	$208.55	$208.60
Purchase #4	$29.62	11.615%	$33.0604	$33.06	$33.05	$33.10
Purchase #5	$211.83	7.783%	$228.3167	$228.32	$228.30	$228.30
Purchase #6	$58.30	5.854%	$61.7129	$61.71	$61.70	$61.70
Purchase #7	$50.26	5.224%	$52.8856	$52.89	$52.90	$52.90
7 purchase totals =	$937.36		$1,002.2580	$1,002.26	$1,002.25	$1,002.30