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	$214.80	8.710%	$233.5091	$233.51	$233.50	$233.50
Purchase #2	$120.83	6.181%	$128.2985	$128.30	$128.30	$128.30
Purchase #3	$178.64	11.842%	$199.7945	$199.79	$199.80	$199.80
Purchase #4	$19.59	11.468%	$21.8366	$21.84	$21.85	$21.80
Purchase #5	$18.50	12.314%	$20.7781	$20.78	$20.80	$20.80
Purchase #6	$58.83	9.478%	$64.4059	$64.41	$64.40	$64.40
Purchase #7	$152.54	5.456%	$160.8626	$160.86	$160.85	$160.90
7 purchase totals =	$763.73		$829.4853	$829.49	$829.50	$829.50