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	$75.82	9.361%	$82.9175	$82.92	$82.90	$82.90
Purchase #2	$77.29	3.239%	$79.7934	$79.79	$79.80	$79.80
Purchase #3	$66.52	6.848%	$71.0753	$71.08	$71.10	$71.10
Purchase #4	$222.80	8.679%	$242.1368	$242.14	$242.15	$242.10
Purchase #5	$188.48	4.120%	$196.2454	$196.25	$196.25	$196.20
Purchase #6	$149.77	8.781%	$162.9213	$162.92	$162.90	$162.90
Purchase #7	$67.31	7.542%	$72.3865	$72.39	$72.40	$72.40
7 purchase totals =	$847.99		$907.4762	$907.49	$907.50	$907.40