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	$215.42	3.366%	$222.671	$222.67	$222.65	$222.70
Purchase #2	$57.95	4.266%	$60.4221	$60.42	$60.40	$60.40
Purchase #3	$200.28	10.233%	$220.7747	$220.77	$220.75	$220.80
Purchase #4	$175.45	5.631%	$185.3296	$185.33	$185.35	$185.30
Purchase #5	$37.80	12.528%	$42.5356	$42.54	$42.55	$42.50
Purchase #6	$68.83	10.871%	$76.3125	$76.31	$76.30	$76.30
Purchase #7	$23.59	7.423%	$25.3411	$25.34	$25.35	$25.30
7 purchase totals =	$779.32		$833.3866	$833.38	$833.35	$833.30