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	$16.93	4.696%	$17.725	$17.73	$17.75	$17.70
Purchase #2	$146.29	11.279%	$162.79	$162.79	$162.80	$162.80
Purchase #3	$21.52	4.598%	$22.5095	$22.51	$22.50	$22.50
Purchase #4	$216.51	11.601%	$241.6273	$241.63	$241.65	$241.60
Purchase #5	$152.25	6.665%	$162.3975	$162.40	$162.40	$162.40
Purchase #6	$72.99	8.163%	$78.9482	$78.95	$78.95	$78.90
Purchase #7	$36.30	3.198%	$37.4609	$37.46	$37.45	$37.50
7 purchase totals =	$662.79		$723.4584	$723.47	$723.50	$723.40