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	$56.54	9.237%	$61.7626	$61.76	$61.75	$61.80
Purchase #2	$134.44	6.782%	$143.5577	$143.56	$143.55	$143.60
Purchase #3	$32.77	6.103%	$34.77	$34.77	$34.75	$34.80
Purchase #4	$192.38	3.526%	$199.1633	$199.16	$199.15	$199.20
Purchase #5	$14.53	7.144%	$15.568	$15.57	$15.55	$15.60
Purchase #6	$200.73	11.338%	$223.4888	$223.49	$223.50	$223.50
Purchase #7	$101.73	4.541%	$106.3496	$106.35	$106.35	$106.30
7 purchase totals =	$733.12		$784.6600	$784.66	$784.60	$784.80