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	$106.49	7.734%	$114.7259	$114.73	$114.75	$114.70
Purchase #2	$151.76	13.623%	$172.4343	$172.43	$172.45	$172.40
Purchase #3	$168.43	3.268%	$173.9343	$173.93	$173.95	$173.90
Purchase #4	$242.27	8.769%	$263.5147	$263.51	$263.50	$263.50
Purchase #5	$51.85	9.364%	$56.7052	$56.71	$56.70	$56.70
Purchase #6	$16.59	10.157%	$18.275	$18.28	$18.30	$18.30
Purchase #7	$93.49	3.123%	$96.4097	$96.41	$96.40	$96.40
7 purchase totals =	$830.88		$895.9991	$896.00	$896.05	$895.90