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	$131.83	10.272%	$145.3716	$145.37	$145.35	$145.40
Purchase #2	$141.72	12.825%	$159.8956	$159.90	$159.90	$159.90
Purchase #3	$49.99	8.705%	$54.3416	$54.34	$54.35	$54.30
Purchase #4	$170.33	12.493%	$191.6093	$191.61	$191.60	$191.60
Purchase #5	$95.42	8.110%	$103.1586	$103.16	$103.15	$103.20
Purchase #6	$90.33	5.117%	$94.9522	$94.95	$94.95	$95.00
Purchase #7	$244.78	5.677%	$258.6762	$258.68	$258.70	$258.70
7 purchase totals =	$924.40		$1,008.0051	$1,008.01	$1,008.00	$1,008.10