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	$226.48	6.383%	$240.9362	$240.94	$240.95	$240.90
Purchase #2	$98.77	10.178%	$108.8228	$108.82	$108.80	$108.80
Purchase #3	$19.72	8.251%	$21.3471	$21.35	$21.35	$21.30
Purchase #4	$25.42	12.800%	$28.6738	$28.67	$28.65	$28.70
Purchase #5	$152.59	4.853%	$159.9952	$160.00	$160.00	$160.00
Purchase #6	$79.82	4.628%	$83.5141	$83.51	$83.50	$83.50
Purchase #7	$94.87	6.303%	$100.8497	$100.85	$100.85	$100.80
7 purchase totals =	$697.67		$744.1389	$744.14	$744.10	$744.00