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	$32.66	8.574%	$35.4603	$35.46	$35.45	$35.50
Purchase #2	$39.95	8.500%	$43.3458	$43.35	$43.35	$43.30
Purchase #3	$59.88	11.288%	$66.6393	$66.64	$66.65	$66.60
Purchase #4	$11.28	4.279%	$11.7627	$11.76	$11.75	$11.80
Purchase #5	$54.90	10.232%	$60.5174	$60.52	$60.50	$60.50
Purchase #6	$79.49	12.843%	$89.6989	$89.70	$89.70	$89.70
Purchase #7	$90.95	13.672%	$103.3847	$103.38	$103.40	$103.40
7 purchase totals =	$369.11		$410.8091	$410.81	$410.80	$410.80