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	$78.40	5.409%	$82.6407	$82.64	$82.65	$82.60
Purchase #2	$98.86	6.436%	$105.2226	$105.22	$105.20	$105.20
Purchase #3	$132.93	13.624%	$151.0404	$151.04	$151.05	$151.00
Purchase #4	$181.92	5.150%	$191.2889	$191.29	$191.30	$191.30
Purchase #5	$249.78	6.684%	$266.4753	$266.48	$266.50	$266.50
Purchase #6	$182.97	12.847%	$206.4762	$206.48	$206.50	$206.50
Purchase #7	$77.44	4.524%	$80.9434	$80.94	$80.95	$80.90
7 purchase totals =	$1,002.30		$1,084.0875	$1,084.09	$1,084.15	$1,084.00