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	$101.37	7.175%	$108.6433	$108.64	$108.65	$108.60
Purchase #2	$212.60	5.802%	$224.9351	$224.94	$224.95	$224.90
Purchase #3	$70.52	3.145%	$72.7379	$72.74	$72.75	$72.70
Purchase #4	$105.60	13.389%	$119.7388	$119.74	$119.75	$119.70
Purchase #5	$195.40	4.790%	$204.7597	$204.76	$204.75	$204.80
Purchase #6	$106.29	5.761%	$112.4134	$112.41	$112.40	$112.40
Purchase #7	$38.42	10.171%	$42.3277	$42.33	$42.35	$42.30
7 purchase totals =	$830.20		$885.5559	$885.56	$885.60	$885.40