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	$80.45	13.788%	$91.5424	$91.54	$91.55	$91.50
Purchase #2	$243.48	10.621%	$269.34	$269.34	$269.35	$269.30
Purchase #3	$33.86	3.291%	$34.9743	$34.97	$34.95	$35.00
Purchase #4	$214.77	4.168%	$223.7216	$223.72	$223.70	$223.70
Purchase #5	$198.85	6.495%	$211.7653	$211.77	$211.75	$211.80
Purchase #6	$191.67	4.267%	$199.8486	$199.85	$199.85	$199.80
Purchase #7	$129.47	9.239%	$141.4317	$141.43	$141.45	$141.40
7 purchase totals =	$1,092.55		$1,172.6239	$1,172.62	$1,172.60	$1,172.50