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	$107.76	6.375%	$114.6297	$114.63	$114.65	$114.60
Purchase #2	$222.56	9.838%	$244.4555	$244.46	$244.45	$244.50
Purchase #3	$75.36	5.271%	$79.3322	$79.33	$79.35	$79.30
Purchase #4	$166.75	3.313%	$172.2744	$172.27	$172.25	$172.30
Purchase #5	$142.95	10.728%	$158.2857	$158.29	$158.30	$158.30
Purchase #6	$136.76	10.275%	$150.8121	$150.81	$150.80	$150.80
Purchase #7	$173.85	3.778%	$180.4181	$180.42	$180.40	$180.40
7 purchase totals =	$1,025.99		$1,100.2077	$1,100.21	$1,100.20	$1,100.20