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	$158.47	6.459%	$168.7056	$168.71	$168.70	$168.70
Purchase #2	$237.86	9.523%	$260.5114	$260.51	$260.50	$260.50
Purchase #3	$90.34	11.711%	$100.9197	$100.92	$100.90	$100.90
Purchase #4	$175.59	13.747%	$199.7284	$199.73	$199.75	$199.70
Purchase #5	$99.98	3.404%	$103.3833	$103.38	$103.40	$103.40
Purchase #6	$207.44	8.769%	$225.6304	$225.63	$225.65	$225.60
Purchase #7	$149.25	9.480%	$163.3989	$163.40	$163.40	$163.40
7 purchase totals =	$1,118.93		$1,222.2777	$1,222.28	$1,222.30	$1,222.20