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	$190.43	12.122%	$213.5139	$213.51	$213.50	$213.50
Purchase #2	$165.73	3.152%	$170.9538	$170.95	$170.95	$171.00
Purchase #3	$43.85	10.410%	$48.4148	$48.41	$48.40	$48.40
Purchase #4	$248.66	3.242%	$256.7216	$256.72	$256.70	$256.70
Purchase #5	$39.71	10.269%	$43.7878	$43.79	$43.80	$43.80
Purchase #6	$95.77	7.776%	$103.2171	$103.22	$103.20	$103.20
Purchase #7	$203.67	9.616%	$223.2549	$223.25	$223.25	$223.30
7 purchase totals =	$987.82		$1,059.8639	$1,059.85	$1,059.80	$1,059.90