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	$143.30	7.523%	$154.0805	$154.08	$154.10	$154.10
Purchase #2	$64.81	3.457%	$67.0505	$67.05	$67.05	$67.10
Purchase #3	$169.28	9.633%	$185.5867	$185.59	$185.60	$185.60
Purchase #4	$229.28	11.298%	$255.1841	$255.18	$255.20	$255.20
Purchase #5	$44.36	8.401%	$48.0867	$48.09	$48.10	$48.10
Purchase #6	$149.48	12.343%	$167.9303	$167.93	$167.95	$167.90
Purchase #7	$151.76	9.498%	$166.1742	$166.17	$166.15	$166.20
7 purchase totals =	$952.27		$1,044.0930	$1,044.09	$1,044.15	$1,044.20