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	$29.86	12.433%	$33.5725	$33.57	$33.55	$33.60
Purchase #2	$162.46	8.286%	$175.9214	$175.92	$175.90	$175.90
Purchase #3	$151.61	4.607%	$158.5947	$158.59	$158.60	$158.60
Purchase #4	$148.70	10.382%	$164.138	$164.14	$164.15	$164.10
Purchase #5	$96.93	5.797%	$102.549	$102.55	$102.55	$102.50
Purchase #6	$188.36	12.194%	$211.3286	$211.33	$211.35	$211.30
Purchase #7	$191.71	13.175%	$216.9678	$216.97	$216.95	$217.00
7 purchase totals =	$969.63		$1,063.0720	$1,063.07	$1,063.05	$1,063.00