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	$126.49	12.506%	$142.3088	$142.31	$142.30	$142.30
Purchase #2	$202.81	9.617%	$222.3142	$222.31	$222.30	$222.30
Purchase #3	$153.30	7.813%	$165.2773	$165.28	$165.30	$165.30
Purchase #4	$235.46	10.463%	$260.0962	$260.10	$260.10	$260.10
Purchase #5	$39.69	10.485%	$43.8515	$43.85	$43.85	$43.90
Purchase #6	$184.30	3.628%	$190.9864	$190.99	$191.00	$191.00
Purchase #7	$72.55	11.553%	$80.9317	$80.93	$80.95	$80.90
7 purchase totals =	$1,014.60		$1,105.7661	$1,105.77	$1,105.80	$1,105.80