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	$233.84	12.186%	$262.3357	$262.34	$262.35	$262.30
Purchase #2	$155.61	11.752%	$173.8973	$173.90	$173.90	$173.90
Purchase #3	$142.52	12.515%	$160.3564	$160.36	$160.35	$160.40
Purchase #4	$57.94	5.348%	$61.0386	$61.04	$61.05	$61.00
Purchase #5	$79.83	11.491%	$89.0033	$89.00	$89.00	$89.00
Purchase #6	$54.69	3.281%	$56.4844	$56.48	$56.50	$56.50
Purchase #7	$154.51	12.135%	$173.2598	$173.26	$173.25	$173.30
7 purchase totals =	$878.94		$976.3755	$976.38	$976.40	$976.40