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	$131.39	11.179%	$146.0781	$146.08	$146.10	$146.10
Purchase #2	$52.79	13.771%	$60.0597	$60.06	$60.05	$60.10
Purchase #3	$71.89	8.854%	$78.2551	$78.26	$78.25	$78.30
Purchase #4	$243.94	6.274%	$259.2448	$259.24	$259.25	$259.20
Purchase #5	$25.68	10.229%	$28.3068	$28.31	$28.30	$28.30
Purchase #6	$126.52	9.804%	$138.924	$138.92	$138.90	$138.90
Purchase #7	$64.41	11.432%	$71.7734	$71.77	$71.75	$71.80
7 purchase totals =	$716.62		$782.6419	$782.64	$782.60	$782.70