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	$183.92	4.315%	$191.8561	$191.86	$191.85	$191.90
Purchase #2	$247.69	3.640%	$256.7059	$256.71	$256.70	$256.70
Purchase #3	$95.26	10.323%	$105.0937	$105.09	$105.10	$105.10
Purchase #4	$182.79	7.204%	$195.9582	$195.96	$195.95	$196.00
Purchase #5	$96.45	7.320%	$103.5101	$103.51	$103.50	$103.50
Purchase #6	$80.42	6.444%	$85.6023	$85.60	$85.60	$85.60
Purchase #7	$22.38	12.577%	$25.1947	$25.19	$25.20	$25.20
7 purchase totals =	$908.91		$963.9210	$963.92	$963.90	$964.00