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	$153.98	5.341%	$162.2041	$162.20	$162.20	$162.20
Purchase #2	$127.29	12.841%	$143.6353	$143.64	$143.65	$143.60
Purchase #3	$127.51	5.653%	$134.7181	$134.72	$134.70	$134.70
Purchase #4	$242.36	4.526%	$253.3292	$253.33	$253.35	$253.30
Purchase #5	$145.50	7.531%	$156.4576	$156.46	$156.45	$156.50
Purchase #6	$172.62	11.126%	$191.8257	$191.83	$191.85	$191.80
Purchase #7	$117.51	11.273%	$130.7569	$130.76	$130.75	$130.80
7 purchase totals =	$1,086.77		$1,172.9269	$1,172.94	$1,172.95	$1,172.90