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	$156.65	6.418%	$166.7038	$166.70	$166.70	$166.70
Purchase #2	$132.95	3.423%	$137.5009	$137.50	$137.50	$137.50
Purchase #3	$124.61	13.369%	$141.2691	$141.27	$141.25	$141.30
Purchase #4	$140.93	7.572%	$151.6012	$151.60	$151.60	$151.60
Purchase #5	$158.93	10.288%	$175.2807	$175.28	$175.30	$175.30
Purchase #6	$82.61	7.813%	$89.0643	$89.06	$89.05	$89.10
Purchase #7	$187.66	6.126%	$199.1561	$199.16	$199.15	$199.20
7 purchase totals =	$984.34		$1,060.5761	$1,060.57	$1,060.55	$1,060.70