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	$66.69	8.301%	$72.2259	$72.23	$72.25	$72.20
Purchase #2	$250.36	3.866%	$260.0389	$260.04	$260.05	$260.00
Purchase #3	$189.91	13.420%	$215.3959	$215.40	$215.40	$215.40
Purchase #4	$57.89	6.271%	$61.5203	$61.52	$61.50	$61.50
Purchase #5	$231.63	10.166%	$255.1775	$255.18	$255.20	$255.20
Purchase #6	$94.54	9.314%	$103.3455	$103.35	$103.35	$103.30
Purchase #7	$193.96	7.617%	$208.7339	$208.73	$208.75	$208.70
7 purchase totals =	$1,084.98		$1,176.4379	$1,176.45	$1,176.50	$1,176.30