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	$101.61	7.366%	$109.0946	$109.09	$109.10	$109.10
Purchase #2	$32.83	7.408%	$35.262	$35.26	$35.25	$35.30
Purchase #3	$145.63	6.847%	$155.6013	$155.60	$155.60	$155.60
Purchase #4	$100.87	10.581%	$111.5431	$111.54	$111.55	$111.50
Purchase #5	$248.44	10.478%	$274.4715	$274.47	$274.45	$274.50
Purchase #6	$162.48	7.184%	$174.1526	$174.15	$174.15	$174.20
Purchase #7	$139.31	13.573%	$158.2185	$158.22	$158.20	$158.20
7 purchase totals =	$931.17		$1,018.3436	$1,018.33	$1,018.30	$1,018.40