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	$131.64	10.810%	$145.8703	$145.87	$145.85	$145.90
Purchase #2	$33.38	13.659%	$37.9394	$37.94	$37.95	$37.90
Purchase #3	$33.34	12.268%	$37.4302	$37.43	$37.45	$37.40
Purchase #4	$222.44	12.634%	$250.5431	$250.54	$250.55	$250.50
Purchase #5	$204.98	11.657%	$228.8745	$228.87	$228.85	$228.90
Purchase #6	$154.92	3.134%	$159.7752	$159.78	$159.80	$159.80
Purchase #7	$226.75	5.172%	$238.4775	$238.48	$238.50	$238.50
7 purchase totals =	$1,007.45		$1,098.9102	$1,098.91	$1,098.95	$1,098.90