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	$185.82	11.750%	$207.6539	$207.65	$207.65	$207.70
Purchase #2	$35.82	4.379%	$37.3886	$37.39	$37.40	$37.40
Purchase #3	$100.71	7.714%	$108.4788	$108.48	$108.50	$108.50
Purchase #4	$19.46	7.304%	$20.8814	$20.88	$20.90	$20.90
Purchase #5	$124.76	6.167%	$132.4539	$132.45	$132.45	$132.50
Purchase #6	$107.69	10.729%	$119.2441	$119.24	$119.25	$119.20
Purchase #7	$148.52	9.538%	$162.6858	$162.69	$162.70	$162.70
7 purchase totals =	$722.78		$788.7865	$788.78	$788.85	$788.90