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	$153.46	12.574%	$172.7561	$172.76	$172.75	$172.80
Purchase #2	$103.98	3.612%	$107.7358	$107.74	$107.75	$107.70
Purchase #3	$116.36	9.199%	$127.064	$127.06	$127.05	$127.10
Purchase #4	$83.28	12.663%	$93.8257	$93.83	$93.85	$93.80
Purchase #5	$11.58	5.551%	$12.2228	$12.22	$12.20	$12.20
Purchase #6	$83.59	3.854%	$86.8116	$86.81	$86.80	$86.80
Purchase #7	$140.57	10.599%	$155.469	$155.47	$155.45	$155.50
7 purchase totals =	$692.82		$755.8850	$755.89	$755.85	$755.90