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	$134.34	13.104%	$151.9439	$151.94	$151.95	$151.90
Purchase #2	$238.86	7.232%	$256.1344	$256.13	$256.15	$256.10
Purchase #3	$85.92	11.215%	$95.5559	$95.56	$95.55	$95.60
Purchase #4	$192.36	3.857%	$199.7793	$199.78	$199.80	$199.80
Purchase #5	$180.72	13.560%	$205.2256	$205.23	$205.25	$205.20
Purchase #6	$13.77	6.788%	$14.7047	$14.70	$14.70	$14.70
Purchase #7	$123.56	11.673%	$137.9832	$137.98	$138.00	$138.00
7 purchase totals =	$969.53		$1,061.3270	$1,061.32	$1,061.40	$1,061.30