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	$46.44	3.526%	$48.0775	$48.08	$48.10	$48.10
Purchase #2	$26.39	4.329%	$27.5324	$27.53	$27.55	$27.50
Purchase #3	$64.66	11.710%	$72.2317	$72.23	$72.25	$72.20
Purchase #4	$154.93	8.285%	$167.766	$167.77	$167.75	$167.80
Purchase #5	$247.47	7.321%	$265.5873	$265.59	$265.60	$265.60
Purchase #6	$143.34	5.384%	$151.0574	$151.06	$151.05	$151.10
Purchase #7	$70.60	13.165%	$79.8945	$79.89	$79.90	$79.90
7 purchase totals =	$753.83		$812.1468	$812.15	$812.20	$812.20