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	$12.46	13.619%	$14.1569	$14.16	$14.15	$14.20
Purchase #2	$138.39	9.440%	$151.454	$151.45	$151.45	$151.50
Purchase #3	$165.60	12.855%	$186.8879	$186.89	$186.90	$186.90
Purchase #4	$184.63	3.197%	$190.5326	$190.53	$190.55	$190.50
Purchase #5	$99.31	12.240%	$111.4655	$111.47	$111.45	$111.50
Purchase #6	$248.97	11.192%	$276.8347	$276.83	$276.85	$276.80
Purchase #7	$159.94	12.258%	$179.5454	$179.55	$179.55	$179.50
7 purchase totals =	$1,009.30		$1,110.8770	$1,110.88	$1,110.90	$1,110.90