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	$92.68	11.434%	$103.277	$103.28	$103.30	$103.30
Purchase #2	$185.76	13.320%	$210.5032	$210.50	$210.50	$210.50
Purchase #3	$42.83	6.767%	$45.7283	$45.73	$45.75	$45.70
Purchase #4	$206.75	8.551%	$224.4292	$224.43	$224.45	$224.40
Purchase #5	$161.28	10.651%	$178.4579	$178.46	$178.45	$178.50
Purchase #6	$89.61	10.579%	$99.0898	$99.09	$99.10	$99.10
Purchase #7	$43.43	5.611%	$45.8669	$45.87	$45.85	$45.90
7 purchase totals =	$822.34		$907.3523	$907.36	$907.40	$907.40