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	$185.87	12.215%	$208.574	$208.57	$208.55	$208.60
Purchase #2	$48.77	11.506%	$54.3815	$54.38	$54.40	$54.40
Purchase #3	$29.66	12.832%	$33.466	$33.47	$33.45	$33.50
Purchase #4	$145.96	5.530%	$154.0316	$154.03	$154.05	$154.00
Purchase #5	$174.88	12.321%	$196.427	$196.43	$196.45	$196.40
Purchase #6	$151.73	4.555%	$158.6413	$158.64	$158.65	$158.60
Purchase #7	$98.39	8.502%	$106.7551	$106.76	$106.75	$106.80
7 purchase totals =	$835.26		$912.2765	$912.28	$912.30	$912.30