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	$65.38	9.659%	$71.6951	$71.70	$71.70	$71.70
Purchase #2	$80.93	3.143%	$83.4736	$83.47	$83.45	$83.50
Purchase #3	$16.69	12.469%	$18.7711	$18.77	$18.75	$18.80
Purchase #4	$65.51	12.693%	$73.8252	$73.83	$73.85	$73.80
Purchase #5	$37.63	10.132%	$41.4427	$41.44	$41.45	$41.40
Purchase #6	$44.32	6.616%	$47.2522	$47.25	$47.25	$47.30
Purchase #7	$20.40	13.107%	$23.0738	$23.07	$23.05	$23.10
7 purchase totals =	$330.86		$359.5337	$359.53	$359.50	$359.60