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	$172.97	13.639%	$196.5614	$196.56	$196.55	$196.60
Purchase #2	$211.45	5.105%	$222.2445	$222.24	$222.25	$222.20
Purchase #3	$170.45	3.269%	$176.022	$176.02	$176.00	$176.00
Purchase #4	$102.68	8.525%	$111.4335	$111.43	$111.45	$111.40
Purchase #5	$95.86	6.220%	$101.8225	$101.82	$101.80	$101.80
Purchase #6	$161.87	11.183%	$179.9719	$179.97	$179.95	$180.00
Purchase #7	$122.78	13.185%	$138.9685	$138.97	$138.95	$139.00
7 purchase totals =	$1,038.06		$1,127.0243	$1,127.01	$1,126.95	$1,127.00