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	$108.93	7.554%	$117.1586	$117.16	$117.15	$117.20
Purchase #2	$81.88	9.304%	$89.4981	$89.50	$89.50	$89.50
Purchase #3	$138.59	11.125%	$154.0081	$154.01	$154.00	$154.00
Purchase #4	$124.72	9.315%	$136.3377	$136.34	$136.35	$136.30
Purchase #5	$170.72	8.181%	$184.6866	$184.69	$184.70	$184.70
Purchase #6	$205.38	4.637%	$214.9035	$214.90	$214.90	$214.90
Purchase #7	$79.76	12.675%	$89.8696	$89.87	$89.85	$89.90
7 purchase totals =	$909.98		$986.4622	$986.47	$986.45	$986.50