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	$32.84	9.123%	$35.836	$35.84	$35.85	$35.80
Purchase #2	$176.94	13.297%	$200.4677	$200.47	$200.45	$200.50
Purchase #3	$218.56	11.524%	$243.7469	$243.75	$243.75	$243.70
Purchase #4	$174.69	11.174%	$194.2099	$194.21	$194.20	$194.20
Purchase #5	$142.29	4.352%	$148.4825	$148.48	$148.50	$148.50
Purchase #6	$11.39	6.213%	$12.0977	$12.10	$12.10	$12.10
Purchase #7	$118.67	7.750%	$127.8669	$127.87	$127.85	$127.90
7 purchase totals =	$875.38		$962.7076	$962.72	$962.70	$962.70