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	$142.96	12.245%	$160.4655	$160.47	$160.45	$160.50
Purchase #2	$6.97	11.653%	$7.7822	$7.78	$7.80	$7.80
Purchase #3	$42.40	10.726%	$46.9478	$46.95	$46.95	$46.90
Purchase #4	$123.82	8.123%	$133.8779	$133.88	$133.90	$133.90
Purchase #5	$122.34	9.177%	$133.5671	$133.57	$133.55	$133.60
Purchase #6	$94.43	5.335%	$99.4678	$99.47	$99.45	$99.50
Purchase #7	$26.61	5.816%	$28.1576	$28.16	$28.15	$28.20
7 purchase totals =	$559.53		$610.2659	$610.28	$610.25	$610.40