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	$168.32	7.462%	$180.88	$180.88	$180.90	$180.90
Purchase #2	$148.60	13.419%	$168.5406	$168.54	$168.55	$168.50
Purchase #3	$173.26	10.768%	$191.9166	$191.92	$191.90	$191.90
Purchase #4	$15.89	10.388%	$17.5407	$17.54	$17.55	$17.50
Purchase #5	$154.85	4.645%	$162.0428	$162.04	$162.05	$162.00
Purchase #6	$203.80	5.661%	$215.3371	$215.34	$215.35	$215.30
Purchase #7	$42.93	9.249%	$46.9006	$46.90	$46.90	$46.90
7 purchase totals =	$907.65		$983.1584	$983.16	$983.20	$983.00