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	$212.87	4.601%	$222.6641	$222.66	$222.65	$222.70
Purchase #2	$102.55	7.713%	$110.4597	$110.46	$110.45	$110.50
Purchase #3	$57.51	13.748%	$65.4165	$65.42	$65.40	$65.40
Purchase #4	$178.77	8.541%	$194.0387	$194.04	$194.05	$194.00
Purchase #5	$103.75	5.425%	$109.3784	$109.38	$109.40	$109.40
Purchase #6	$123.38	4.515%	$128.9506	$128.95	$128.95	$129.00
Purchase #7	$138.80	4.660%	$145.2681	$145.27	$145.25	$145.30
7 purchase totals =	$917.63		$976.1761	$976.18	$976.15	$976.30