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	$13.72	3.539%	$14.2056	$14.21	$14.20	$14.20
Purchase #2	$13.76	12.295%	$15.4518	$15.45	$15.45	$15.50
Purchase #3	$38.29	7.731%	$41.2502	$41.25	$41.25	$41.30
Purchase #4	$64.67	3.201%	$66.7401	$66.74	$66.75	$66.70
Purchase #5	$128.92	12.108%	$144.5296	$144.53	$144.55	$144.50
Purchase #6	$153.79	10.627%	$170.1333	$170.13	$170.15	$170.10
Purchase #7	$52.87	13.356%	$59.9313	$59.93	$59.95	$59.90
7 purchase totals =	$466.02		$512.2419	$512.24	$512.30	$512.20