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	$179.37	7.448%	$192.7295	$192.73	$192.75	$192.70
Purchase #2	$29.91	9.615%	$32.7858	$32.79	$32.80	$32.80
Purchase #3	$141.50	12.752%	$159.5441	$159.54	$159.55	$159.50
Purchase #4	$40.47	4.739%	$42.3879	$42.39	$42.40	$42.40
Purchase #5	$122.29	13.469%	$138.7612	$138.76	$138.75	$138.80
Purchase #6	$231.47	10.313%	$255.3415	$255.34	$255.35	$255.30
Purchase #7	$87.98	12.571%	$99.04	$99.04	$99.05	$99.00
7 purchase totals =	$832.99		$920.5900	$920.59	$920.65	$920.50