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	$190.30	12.532%	$214.1484	$214.15	$214.15	$214.10
Purchase #2	$215.90	12.682%	$243.2804	$243.28	$243.30	$243.30
Purchase #3	$27.87	7.535%	$29.97	$29.97	$29.95	$30.00
Purchase #4	$95.81	9.137%	$104.5642	$104.56	$104.55	$104.60
Purchase #5	$19.78	5.421%	$20.8523	$20.85	$20.85	$20.90
Purchase #6	$30.43	6.852%	$32.5151	$32.52	$32.50	$32.50
Purchase #7	$49.56	10.104%	$54.5675	$54.57	$54.55	$54.60
7 purchase totals =	$629.65		$699.8979	$699.90	$699.85	$700.00