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	$105.38	3.837%	$109.4234	$109.42	$109.40	$109.40
Purchase #2	$111.73	9.641%	$122.5019	$122.50	$122.50	$122.50
Purchase #3	$95.92	11.821%	$107.2587	$107.26	$107.25	$107.30
Purchase #4	$33.33	6.361%	$35.4501	$35.45	$35.45	$35.50
Purchase #5	$113.49	4.255%	$118.319	$118.32	$118.30	$118.30
Purchase #6	$58.76	10.728%	$65.0638	$65.06	$65.05	$65.10
Purchase #7	$91.64	4.210%	$95.498	$95.50	$95.50	$95.50
7 purchase totals =	$610.25		$653.5149	$653.51	$653.45	$653.60