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	$219.65	9.788%	$241.1493	$241.15	$241.15	$241.10
Purchase #2	$137.80	11.658%	$153.8647	$153.86	$153.85	$153.90
Purchase #3	$148.85	4.696%	$155.84	$155.84	$155.85	$155.80
Purchase #4	$182.71	4.757%	$191.4015	$191.40	$191.40	$191.40
Purchase #5	$46.50	7.400%	$49.941	$49.94	$49.95	$49.90
Purchase #6	$139.31	8.564%	$151.2405	$151.24	$151.25	$151.20
Purchase #7	$188.81	4.239%	$196.8137	$196.81	$196.80	$196.80
7 purchase totals =	$1,063.63		$1,140.2507	$1,140.24	$1,140.25	$1,140.10