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	$93.30	10.736%	$103.3167	$103.32	$103.30	$103.30
Purchase #2	$127.50	5.270%	$134.2193	$134.22	$134.20	$134.20
Purchase #3	$167.31	11.184%	$186.022	$186.02	$186.00	$186.00
Purchase #4	$234.80	8.439%	$254.6148	$254.61	$254.60	$254.60
Purchase #5	$32.82	13.201%	$37.1526	$37.15	$37.15	$37.20
Purchase #6	$246.83	10.201%	$272.0091	$272.01	$272.00	$272.00
Purchase #7	$91.85	8.873%	$99.9999	$100.00	$100.00	$100.00
7 purchase totals =	$994.41		$1,087.3344	$1,087.33	$1,087.25	$1,087.30