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	$199.57	4.763%	$209.0755	$209.08	$209.10	$209.10
Purchase #2	$136.71	10.546%	$151.1274	$151.13	$151.15	$151.10
Purchase #3	$140.94	13.108%	$159.4144	$159.41	$159.40	$159.40
Purchase #4	$180.37	3.438%	$186.5711	$186.57	$186.55	$186.60
Purchase #5	$242.86	5.527%	$256.2829	$256.28	$256.30	$256.30
Purchase #6	$158.67	12.506%	$178.5133	$178.51	$178.50	$178.50
Purchase #7	$149.62	4.856%	$156.8855	$156.89	$156.90	$156.90
7 purchase totals =	$1,208.74		$1,297.8701	$1,297.87	$1,297.90	$1,297.90