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	$151.26	11.138%	$168.1073	$168.11	$168.10	$168.10
Purchase #2	$167.25	5.129%	$175.8283	$175.83	$175.85	$175.80
Purchase #3	$37.32	13.614%	$42.4007	$42.40	$42.40	$42.40
Purchase #4	$217.75	3.811%	$226.0485	$226.05	$226.05	$226.00
Purchase #5	$208.58	6.587%	$222.3192	$222.32	$222.30	$222.30
Purchase #6	$96.60	3.617%	$100.094	$100.09	$100.10	$100.10
Purchase #7	$137.31	11.695%	$153.3684	$153.37	$153.35	$153.40
7 purchase totals =	$1,016.07		$1,088.1664	$1,088.17	$1,088.15	$1,088.10