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	$140.28	3.661%	$145.4157	$145.42	$145.40	$145.40
Purchase #2	$206.26	7.798%	$222.3442	$222.34	$222.35	$222.30
Purchase #3	$154.64	11.460%	$172.3617	$172.36	$172.35	$172.40
Purchase #4	$236.80	6.297%	$251.7113	$251.71	$251.70	$251.70
Purchase #5	$84.82	8.821%	$92.302	$92.30	$92.30	$92.30
Purchase #6	$46.58	11.267%	$51.8282	$51.83	$51.85	$51.80
Purchase #7	$241.62	9.541%	$264.673	$264.67	$264.65	$264.70
7 purchase totals =	$1,111.00		$1,200.6361	$1,200.63	$1,200.60	$1,200.60