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	$102.47	3.652%	$106.2122	$106.21	$106.20	$106.20
Purchase #2	$48.34	4.535%	$50.5322	$50.53	$50.55	$50.50
Purchase #3	$144.38	12.698%	$162.7134	$162.71	$162.70	$162.70
Purchase #4	$44.87	6.477%	$47.7762	$47.78	$47.80	$47.80
Purchase #5	$179.33	9.366%	$196.126	$196.13	$196.15	$196.10
Purchase #6	$54.94	11.267%	$61.1301	$61.13	$61.15	$61.10
Purchase #7	$12.75	9.853%	$14.0063	$14.01	$14.00	$14.00
7 purchase totals =	$587.08		$638.4964	$638.50	$638.55	$638.40