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	$211.59	5.596%	$223.4306	$223.43	$223.45	$223.40
Purchase #2	$104.48	4.470%	$109.1503	$109.15	$109.15	$109.20
Purchase #3	$77.49	5.103%	$81.4443	$81.44	$81.45	$81.40
Purchase #4	$176.89	10.127%	$194.8037	$194.80	$194.80	$194.80
Purchase #5	$165.39	6.121%	$175.5135	$175.51	$175.50	$175.50
Purchase #6	$172.65	6.272%	$183.4786	$183.48	$183.50	$183.50
Purchase #7	$49.71	9.328%	$54.3469	$54.35	$54.35	$54.30
7 purchase totals =	$958.20		$1,022.1679	$1,022.16	$1,022.20	$1,022.10