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	$91.91	13.775%	$104.5706	$104.57	$104.55	$104.60
Purchase #2	$248.88	9.118%	$271.5729	$271.57	$271.55	$271.60
Purchase #3	$184.88	7.576%	$198.8865	$198.89	$198.90	$198.90
Purchase #4	$235.85	8.375%	$255.6024	$255.60	$255.60	$255.60
Purchase #5	$21.86	10.333%	$24.1188	$24.12	$24.10	$24.10
Purchase #6	$137.59	10.340%	$151.8168	$151.82	$151.80	$151.80
Purchase #7	$238.65	3.397%	$246.7569	$246.76	$246.75	$246.80
7 purchase totals =	$1,159.62		$1,253.3249	$1,253.33	$1,253.25	$1,253.40