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	$129.99	7.739%	$140.0499	$140.05	$140.05	$140.00
Purchase #2	$171.47	6.496%	$182.6087	$182.61	$182.60	$182.60
Purchase #3	$123.93	6.175%	$131.5827	$131.58	$131.60	$131.60
Purchase #4	$56.89	7.722%	$61.283	$61.28	$61.30	$61.30
Purchase #5	$40.32	11.599%	$44.9967	$45.00	$45.00	$45.00
Purchase #6	$30.68	12.422%	$34.4911	$34.49	$34.50	$34.50
Purchase #7	$179.44	4.386%	$187.3102	$187.31	$187.30	$187.30
7 purchase totals =	$732.72		$782.3223	$782.32	$782.35	$782.30