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	$199.39	11.761%	$222.8403	$222.84	$222.85	$222.80
Purchase #2	$102.50	4.858%	$107.4795	$107.48	$107.50	$107.50
Purchase #3	$212.90	4.480%	$222.4379	$222.44	$222.45	$222.40
Purchase #4	$66.61	11.134%	$74.0264	$74.03	$74.05	$74.00
Purchase #5	$125.46	12.728%	$141.4285	$141.43	$141.45	$141.40
Purchase #6	$208.55	7.728%	$224.6667	$224.67	$224.65	$224.70
Purchase #7	$146.54	13.107%	$165.747	$165.75	$165.75	$165.70
7 purchase totals =	$1,061.95		$1,158.6263	$1,158.64	$1,158.70	$1,158.50