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	$119.28	9.532%	$130.6498	$130.65	$130.65	$130.60
Purchase #2	$114.52	5.146%	$120.4132	$120.41	$120.40	$120.40
Purchase #3	$111.90	6.830%	$119.5428	$119.54	$119.55	$119.50
Purchase #4	$103.46	13.113%	$117.0267	$117.03	$117.05	$117.00
Purchase #5	$15.78	5.488%	$16.646	$16.65	$16.65	$16.60
Purchase #6	$37.38	11.738%	$41.7677	$41.77	$41.75	$41.80
Purchase #7	$56.45	4.635%	$59.0665	$59.07	$59.05	$59.10
7 purchase totals =	$558.77		$605.1127	$605.12	$605.10	$605.00