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	$167.31	13.582%	$190.034	$190.03	$190.05	$190.00
Purchase #2	$163.73	4.854%	$171.6775	$171.68	$171.70	$171.70
Purchase #3	$103.57	7.427%	$111.2621	$111.26	$111.25	$111.30
Purchase #4	$114.29	12.258%	$128.2997	$128.30	$128.30	$128.30
Purchase #5	$53.49	11.235%	$59.4996	$59.50	$59.50	$59.50
Purchase #6	$160.75	13.259%	$182.0638	$182.06	$182.05	$182.10
Purchase #7	$136.33	5.801%	$144.2385	$144.24	$144.25	$144.20
7 purchase totals =	$899.47		$987.0752	$987.07	$987.10	$987.10