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	$171.65	10.421%	$189.5376	$189.54	$189.55	$189.50
Purchase #2	$238.96	7.774%	$257.5368	$257.54	$257.55	$257.50
Purchase #3	$42.25	4.563%	$44.1779	$44.18	$44.20	$44.20
Purchase #4	$119.87	5.584%	$126.5635	$126.56	$126.55	$126.60
Purchase #5	$90.41	5.238%	$95.1457	$95.15	$95.15	$95.10
Purchase #6	$151.72	13.677%	$172.4707	$172.47	$172.45	$172.50
Purchase #7	$171.96	9.583%	$188.4389	$188.44	$188.45	$188.40
7 purchase totals =	$986.82		$1,073.8711	$1,073.88	$1,073.90	$1,073.80