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	$148.30	11.843%	$165.8632	$165.86	$165.85	$165.90
Purchase #2	$180.95	4.370%	$188.8575	$188.86	$188.85	$188.90
Purchase #3	$48.62	13.192%	$55.034	$55.03	$55.05	$55.00
Purchase #4	$122.84	3.578%	$127.2352	$127.24	$127.25	$127.20
Purchase #5	$173.89	5.852%	$184.066	$184.07	$184.05	$184.10
Purchase #6	$114.62	7.623%	$123.3575	$123.36	$123.35	$123.40
Purchase #7	$191.62	3.485%	$198.298	$198.30	$198.30	$198.30
7 purchase totals =	$980.84		$1,042.7114	$1,042.72	$1,042.70	$1,042.80