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	$43.25	4.368%	$45.1392	$45.14	$45.15	$45.10
Purchase #2	$130.87	13.643%	$148.7246	$148.72	$148.70	$148.70
Purchase #3	$228.95	4.866%	$240.0907	$240.09	$240.10	$240.10
Purchase #4	$194.58	7.718%	$209.5977	$209.60	$209.60	$209.60
Purchase #5	$186.64	13.195%	$211.2671	$211.27	$211.25	$211.30
Purchase #6	$46.39	9.679%	$50.8801	$50.88	$50.90	$50.90
Purchase #7	$64.54	12.392%	$72.5378	$72.54	$72.55	$72.50
7 purchase totals =	$895.22		$978.2372	$978.24	$978.25	$978.20