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	$129.95	11.469%	$144.854	$144.85	$144.85	$144.90
Purchase #2	$29.79	9.395%	$32.5888	$32.59	$32.60	$32.60
Purchase #3	$94.27	8.712%	$102.4828	$102.48	$102.50	$102.50
Purchase #4	$123.46	6.337%	$131.2837	$131.28	$131.30	$131.30
Purchase #5	$220.98	9.794%	$242.6228	$242.62	$242.60	$242.60
Purchase #6	$106.59	7.197%	$114.2613	$114.26	$114.25	$114.30
Purchase #7	$180.67	10.754%	$200.0993	$200.10	$200.10	$200.10
7 purchase totals =	$885.71		$968.1927	$968.18	$968.20	$968.30