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	$42.81	3.374%	$44.2544	$44.25	$44.25	$44.30
Purchase #2	$26.44	3.406%	$27.3405	$27.34	$27.35	$27.30
Purchase #3	$38.91	5.477%	$41.0411	$41.04	$41.05	$41.00
Purchase #4	$106.48	10.314%	$117.4623	$117.46	$117.45	$117.50
Purchase #5	$105.37	3.598%	$109.1612	$109.16	$109.15	$109.20
Purchase #6	$123.93	12.543%	$139.4745	$139.47	$139.45	$139.50
Purchase #7	$18.39	13.648%	$20.8999	$20.90	$20.90	$20.90
7 purchase totals =	$462.33		$499.6339	$499.62	$499.60	$499.70