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	$68.53	13.195%	$77.5725	$77.57	$77.55	$77.60
Purchase #2	$174.94	3.278%	$180.6745	$180.67	$180.65	$180.70
Purchase #3	$108.84	3.624%	$112.7844	$112.78	$112.80	$112.80
Purchase #4	$125.59	7.446%	$134.9414	$134.94	$134.95	$134.90
Purchase #5	$138.83	8.356%	$150.4306	$150.43	$150.45	$150.40
Purchase #6	$31.50	6.820%	$33.6483	$33.65	$33.65	$33.60
Purchase #7	$64.49	10.739%	$71.4156	$71.42	$71.40	$71.40
7 purchase totals =	$712.72		$761.4673	$761.46	$761.45	$761.40