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	$111.82	5.605%	$118.0875	$118.09	$118.10	$118.10
Purchase #2	$128.33	13.148%	$145.2028	$145.20	$145.20	$145.20
Purchase #3	$126.94	11.451%	$141.4759	$141.48	$141.50	$141.50
Purchase #4	$224.83	4.647%	$235.2779	$235.28	$235.30	$235.30
Purchase #5	$57.73	3.744%	$59.8914	$59.89	$59.90	$59.90
Purchase #6	$147.98	8.181%	$160.0862	$160.09	$160.10	$160.10
Purchase #7	$44.81	8.262%	$48.5122	$48.51	$48.50	$48.50
7 purchase totals =	$842.44		$908.5339	$908.54	$908.60	$908.60