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	$22.42	13.457%	$25.4371	$25.44	$25.45	$25.40
Purchase #2	$54.96	9.803%	$60.3477	$60.35	$60.35	$60.30
Purchase #3	$68.42	4.788%	$71.6959	$71.70	$71.70	$71.70
Purchase #4	$91.43	9.216%	$99.8562	$99.86	$99.85	$99.90
Purchase #5	$163.94	3.365%	$169.4566	$169.46	$169.45	$169.50
Purchase #6	$140.89	5.367%	$148.4516	$148.45	$148.45	$148.50
Purchase #7	$14.36	12.808%	$16.1992	$16.20	$16.20	$16.20
7 purchase totals =	$556.42		$591.4443	$591.46	$591.45	$591.50