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	$139.29	5.465%	$146.9022	$146.90	$146.90	$146.90
Purchase #2	$55.43	11.756%	$61.9464	$61.95	$61.95	$61.90
Purchase #3	$230.58	10.374%	$254.5004	$254.50	$254.50	$254.50
Purchase #4	$178.38	5.447%	$188.0964	$188.10	$188.10	$188.10
Purchase #5	$160.92	5.598%	$169.9283	$169.93	$169.95	$169.90
Purchase #6	$143.38	13.170%	$162.2631	$162.26	$162.25	$162.30
Purchase #7	$179.81	6.188%	$190.9366	$190.94	$190.95	$190.90
7 purchase totals =	$1,087.79		$1,174.5734	$1,174.58	$1,174.60	$1,174.50