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	$101.62	3.659%	$105.3383	$105.34	$105.35	$105.30
Purchase #2	$77.43	5.209%	$81.4633	$81.46	$81.45	$81.50
Purchase #3	$17.69	4.478%	$18.4822	$18.48	$18.50	$18.50
Purchase #4	$100.37	4.414%	$104.8003	$104.80	$104.80	$104.80
Purchase #5	$179.36	6.805%	$191.5654	$191.57	$191.55	$191.60
Purchase #6	$134.46	12.257%	$150.9408	$150.94	$150.95	$150.90
Purchase #7	$62.78	9.214%	$68.5645	$68.56	$68.55	$68.60
7 purchase totals =	$673.71		$721.1548	$721.15	$721.15	$721.20