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	$245.43	12.324%	$275.6768	$275.68	$275.70	$275.70
Purchase #2	$192.28	3.797%	$199.5809	$199.58	$199.60	$199.60
Purchase #3	$39.70	13.126%	$44.911	$44.91	$44.90	$44.90
Purchase #4	$42.72	8.348%	$46.2863	$46.29	$46.30	$46.30
Purchase #5	$67.50	7.795%	$72.7616	$72.76	$72.75	$72.80
Purchase #6	$25.52	12.116%	$28.612	$28.61	$28.60	$28.60
Purchase #7	$125.90	6.347%	$133.8909	$133.89	$133.90	$133.90
7 purchase totals =	$739.05		$801.7195	$801.72	$801.75	$801.80