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	$241.31	9.329%	$263.8218	$263.82	$263.80	$263.80
Purchase #2	$49.88	7.800%	$53.7706	$53.77	$53.75	$53.80
Purchase #3	$31.29	4.613%	$32.7334	$32.73	$32.75	$32.70
Purchase #4	$67.58	9.648%	$74.1001	$74.10	$74.10	$74.10
Purchase #5	$63.69	4.433%	$66.5134	$66.51	$66.50	$66.50
Purchase #6	$212.29	5.287%	$223.5138	$223.51	$223.50	$223.50
Purchase #7	$46.68	11.609%	$52.0991	$52.10	$52.10	$52.10
7 purchase totals =	$712.72		$766.5522	$766.54	$766.50	$766.50