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	$207.88	13.200%	$235.3202	$235.32	$235.30	$235.30
Purchase #2	$94.33	11.670%	$105.3383	$105.34	$105.35	$105.30
Purchase #3	$46.89	12.698%	$52.8441	$52.84	$52.85	$52.80
Purchase #4	$86.77	8.652%	$94.2773	$94.28	$94.30	$94.30
Purchase #5	$19.65	10.773%	$21.7669	$21.77	$21.75	$21.80
Purchase #6	$187.53	10.462%	$207.1494	$207.15	$207.15	$207.10
Purchase #7	$77.46	6.649%	$82.6103	$82.61	$82.60	$82.60
7 purchase totals =	$720.51		$799.3065	$799.31	$799.30	$799.20