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	$16.57	6.288%	$17.6119	$17.61	$17.60	$17.60
Purchase #2	$195.40	10.199%	$215.3288	$215.33	$215.35	$215.30
Purchase #3	$58.94	5.701%	$62.3002	$62.30	$62.30	$62.30
Purchase #4	$93.84	6.838%	$100.2568	$100.26	$100.25	$100.30
Purchase #5	$123.72	13.116%	$139.9471	$139.95	$139.95	$139.90
Purchase #6	$86.41	4.431%	$90.2388	$90.24	$90.25	$90.20
Purchase #7	$238.25	5.174%	$250.5771	$250.58	$250.60	$250.60
7 purchase totals =	$813.13		$876.2607	$876.27	$876.30	$876.20