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	$183.41	4.649%	$191.9367	$191.94	$191.95	$191.90
Purchase #2	$145.88	11.466%	$162.6066	$162.61	$162.60	$162.60
Purchase #3	$148.83	6.310%	$158.2212	$158.22	$158.20	$158.20
Purchase #4	$145.79	3.492%	$150.881	$150.88	$150.90	$150.90
Purchase #5	$54.36	10.114%	$59.858	$59.86	$59.85	$59.90
Purchase #6	$213.68	8.259%	$231.3278	$231.33	$231.35	$231.30
Purchase #7	$142.50	7.634%	$153.3785	$153.38	$153.40	$153.40
7 purchase totals =	$1,034.45		$1,108.2098	$1,108.22	$1,108.25	$1,108.20