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	$202.59	11.626%	$226.1431	$226.14	$226.15	$226.10
Purchase #2	$56.55	5.731%	$59.7909	$59.79	$59.80	$59.80
Purchase #3	$140.30	5.764%	$148.3869	$148.39	$148.40	$148.40
Purchase #4	$117.90	5.553%	$124.447	$124.45	$124.45	$124.40
Purchase #5	$247.37	13.439%	$280.6141	$280.61	$280.60	$280.60
Purchase #6	$134.84	12.581%	$151.8042	$151.80	$151.80	$151.80
Purchase #7	$246.89	13.466%	$280.1362	$280.14	$280.15	$280.10
7 purchase totals =	$1,146.44		$1,271.3224	$1,271.32	$1,271.35	$1,271.20