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	$163.78	9.322%	$179.0476	$179.05	$179.05	$179.00
Purchase #2	$178.94	3.545%	$185.2834	$185.28	$185.30	$185.30
Purchase #3	$129.66	10.790%	$143.6503	$143.65	$143.65	$143.70
Purchase #4	$211.48	9.622%	$231.8286	$231.83	$231.85	$231.80
Purchase #5	$47.58	7.503%	$51.1499	$51.15	$51.15	$51.10
Purchase #6	$85.31	10.387%	$94.1711	$94.17	$94.15	$94.20
Purchase #7	$81.83	11.872%	$91.5449	$91.54	$91.55	$91.50
7 purchase totals =	$898.58		$976.6758	$976.67	$976.70	$976.60