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	$211.98	5.171%	$222.9415	$222.94	$222.95	$222.90
Purchase #2	$99.89	13.710%	$113.5849	$113.58	$113.60	$113.60
Purchase #3	$48.26	6.262%	$51.282	$51.28	$51.30	$51.30
Purchase #4	$40.77	8.758%	$44.3406	$44.34	$44.35	$44.30
Purchase #5	$147.40	7.730%	$158.794	$158.79	$158.80	$158.80
Purchase #6	$79.64	4.221%	$83.0016	$83.00	$83.00	$83.00
Purchase #7	$103.59	6.618%	$110.4456	$110.45	$110.45	$110.40
7 purchase totals =	$731.53		$784.3902	$784.38	$784.45	$784.30