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	$171.60	8.196%	$185.6643	$185.66	$185.65	$185.70
Purchase #2	$109.69	9.222%	$119.8056	$119.81	$119.80	$119.80
Purchase #3	$182.89	7.173%	$196.0087	$196.01	$196.00	$196.00
Purchase #4	$214.55	10.821%	$237.7665	$237.77	$237.75	$237.80
Purchase #5	$58.67	7.717%	$63.1976	$63.20	$63.20	$63.20
Purchase #6	$172.60	13.410%	$195.7457	$195.75	$195.75	$195.70
Purchase #7	$94.69	6.265%	$100.6223	$100.62	$100.60	$100.60
7 purchase totals =	$1,004.69		$1,098.8107	$1,098.82	$1,098.75	$1,098.80