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	$106.92	5.197%	$112.4766	$112.48	$112.50	$112.50
Purchase #2	$51.54	3.294%	$53.2377	$53.24	$53.25	$53.20
Purchase #3	$98.85	6.582%	$105.3563	$105.36	$105.35	$105.40
Purchase #4	$36.38	8.379%	$39.4283	$39.43	$39.45	$39.40
Purchase #5	$53.73	6.665%	$57.3111	$57.31	$57.30	$57.30
Purchase #6	$73.42	6.194%	$77.9676	$77.97	$77.95	$78.00
Purchase #7	$224.99	13.202%	$254.6932	$254.69	$254.70	$254.70
7 purchase totals =	$645.83		$700.4708	$700.48	$700.50	$700.50