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	$151.68	8.520%	$164.6031	$164.60	$164.60	$164.60
Purchase #2	$206.95	13.745%	$235.3953	$235.40	$235.40	$235.40
Purchase #3	$213.52	4.165%	$222.4131	$222.41	$222.40	$222.40
Purchase #4	$79.98	10.436%	$88.3267	$88.33	$88.35	$88.30
Purchase #5	$184.58	11.229%	$205.3065	$205.31	$205.30	$205.30
Purchase #6	$225.35	13.208%	$255.1142	$255.11	$255.10	$255.10
Purchase #7	$233.28	11.388%	$259.8459	$259.85	$259.85	$259.80
7 purchase totals =	$1,295.34		$1,431.0048	$1,431.01	$1,431.00	$1,430.90