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	$103.36	6.384%	$109.9585	$109.96	$109.95	$110.00
Purchase #2	$106.68	5.471%	$112.5165	$112.52	$112.50	$112.50
Purchase #3	$45.47	12.409%	$51.1124	$51.11	$51.10	$51.10
Purchase #4	$210.99	7.742%	$227.3248	$227.32	$227.30	$227.30
Purchase #5	$14.52	8.632%	$15.7734	$15.77	$15.75	$15.80
Purchase #6	$138.70	10.201%	$152.8488	$152.85	$152.85	$152.80
Purchase #7	$101.82	7.464%	$109.4198	$109.42	$109.40	$109.40
7 purchase totals =	$721.54		$778.9542	$778.95	$778.85	$778.90