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	$72.92	3.262%	$75.2987	$75.30	$75.30	$75.30
Purchase #2	$233.69	9.749%	$256.4724	$256.47	$256.45	$256.50
Purchase #3	$214.50	6.425%	$228.2816	$228.28	$228.30	$228.30
Purchase #4	$7.44	5.603%	$7.8569	$7.86	$7.85	$7.90
Purchase #5	$163.73	7.244%	$175.5906	$175.59	$175.60	$175.60
Purchase #6	$55.32	4.564%	$57.8448	$57.84	$57.85	$57.80
Purchase #7	$226.65	12.234%	$254.3784	$254.38	$254.40	$254.40
7 purchase totals =	$974.25		$1,055.7234	$1,055.72	$1,055.75	$1,055.80