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	$44.90	10.106%	$49.4376	$49.44	$49.45	$49.40
Purchase #2	$194.91	11.393%	$217.1161	$217.12	$217.10	$217.10
Purchase #3	$67.94	13.581%	$77.1669	$77.17	$77.15	$77.20
Purchase #4	$131.91	4.297%	$137.5782	$137.58	$137.60	$137.60
Purchase #5	$97.70	6.702%	$104.2479	$104.25	$104.25	$104.20
Purchase #6	$55.33	8.227%	$59.882	$59.88	$59.90	$59.90
Purchase #7	$213.33	11.613%	$238.104	$238.10	$238.10	$238.10
7 purchase totals =	$806.02		$883.5327	$883.54	$883.55	$883.50