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	$136.38	12.498%	$153.4248	$153.42	$153.40	$153.40
Purchase #2	$215.88	3.209%	$222.8076	$222.81	$222.80	$222.80
Purchase #3	$95.83	4.784%	$100.4145	$100.41	$100.40	$100.40
Purchase #4	$132.73	7.560%	$142.7644	$142.76	$142.75	$142.80
Purchase #5	$230.94	12.857%	$260.632	$260.63	$260.65	$260.60
Purchase #6	$130.71	6.135%	$138.7291	$138.73	$138.75	$138.70
Purchase #7	$210.54	4.152%	$219.2816	$219.28	$219.30	$219.30
7 purchase totals =	$1,153.01		$1,238.0540	$1,238.04	$1,238.05	$1,238.00