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	$66.92	3.233%	$69.0835	$69.08	$69.10	$69.10
Purchase #2	$250.62	3.552%	$259.522	$259.52	$259.50	$259.50
Purchase #3	$175.95	8.711%	$191.277	$191.28	$191.30	$191.30
Purchase #4	$37.25	10.401%	$41.1244	$41.12	$41.10	$41.10
Purchase #5	$101.79	12.259%	$114.2684	$114.27	$114.25	$114.30
Purchase #6	$131.64	6.141%	$139.724	$139.72	$139.70	$139.70
Purchase #7	$34.61	9.357%	$37.8485	$37.85	$37.85	$37.80
7 purchase totals =	$798.78		$852.8478	$852.84	$852.80	$852.80