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	$159.96	3.388%	$165.3794	$165.38	$165.40	$165.40
Purchase #2	$195.64	3.789%	$203.0528	$203.05	$203.05	$203.10
Purchase #3	$38.57	12.762%	$43.4923	$43.49	$43.50	$43.50
Purchase #4	$121.45	4.654%	$127.1023	$127.10	$127.10	$127.10
Purchase #5	$132.71	13.842%	$151.0797	$151.08	$151.10	$151.10
Purchase #6	$233.50	7.653%	$251.3698	$251.37	$251.35	$251.40
Purchase #7	$36.91	10.782%	$40.8896	$40.89	$40.90	$40.90
7 purchase totals =	$918.74		$982.3659	$982.36	$982.40	$982.50