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	$111.82	6.844%	$119.473	$119.47	$119.45	$119.50
Purchase #2	$114.77	3.665%	$118.9763	$118.98	$119.00	$119.00
Purchase #3	$206.91	12.506%	$232.7862	$232.79	$232.80	$232.80
Purchase #4	$36.50	10.346%	$40.2763	$40.28	$40.30	$40.30
Purchase #5	$144.39	12.528%	$162.4792	$162.48	$162.50	$162.50
Purchase #6	$34.56	3.491%	$35.7665	$35.77	$35.75	$35.80
Purchase #7	$105.43	5.557%	$111.2887	$111.29	$111.30	$111.30
7 purchase totals =	$754.38		$821.0462	$821.06	$821.10	$821.20