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	$95.72	4.699%	$100.2179	$100.22	$100.20	$100.20
Purchase #2	$180.82	13.783%	$205.7424	$205.74	$205.75	$205.70
Purchase #3	$60.52	7.196%	$64.875	$64.88	$64.90	$64.90
Purchase #4	$144.25	3.272%	$148.9699	$148.97	$148.95	$149.00
Purchase #5	$207.81	4.355%	$216.8601	$216.86	$216.85	$216.90
Purchase #6	$151.58	3.497%	$156.8808	$156.88	$156.90	$156.90
Purchase #7	$17.80	6.325%	$18.9259	$18.93	$18.95	$18.90
7 purchase totals =	$858.50		$912.4720	$912.48	$912.50	$912.50