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	$54.64	4.588%	$57.1469	$57.15	$57.15	$57.10
Purchase #2	$29.71	9.329%	$32.4816	$32.48	$32.50	$32.50
Purchase #3	$88.64	12.430%	$99.658	$99.66	$99.65	$99.70
Purchase #4	$247.83	7.536%	$266.5065	$266.51	$266.50	$266.50
Purchase #5	$121.28	5.321%	$127.7333	$127.73	$127.75	$127.70
Purchase #6	$186.64	11.659%	$208.4004	$208.40	$208.40	$208.40
Purchase #7	$211.84	9.269%	$231.4754	$231.48	$231.50	$231.50
7 purchase totals =	$940.58		$1,023.4021	$1,023.41	$1,023.45	$1,023.40