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	$149.49	8.209%	$161.7616	$161.76	$161.75	$161.80
Purchase #2	$199.70	10.711%	$221.0899	$221.09	$221.10	$221.10
Purchase #3	$145.88	5.549%	$153.9749	$153.97	$153.95	$154.00
Purchase #4	$248.85	9.259%	$271.891	$271.89	$271.90	$271.90
Purchase #5	$65.72	11.769%	$73.4546	$73.45	$73.45	$73.50
Purchase #6	$37.88	10.262%	$41.7672	$41.77	$41.75	$41.80
Purchase #7	$49.63	9.765%	$54.4764	$54.48	$54.50	$54.50
7 purchase totals =	$897.15		$978.4156	$978.41	$978.40	$978.60