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	$12.94	13.730%	$14.7167	$14.72	$14.70	$14.70
Purchase #2	$133.66	3.595%	$138.4651	$138.47	$138.45	$138.50
Purchase #3	$98.82	7.653%	$106.3827	$106.38	$106.40	$106.40
Purchase #4	$16.38	10.269%	$18.0621	$18.06	$18.05	$18.10
Purchase #5	$74.66	10.216%	$82.2873	$82.29	$82.30	$82.30
Purchase #6	$172.78	8.785%	$187.9587	$187.96	$187.95	$188.00
Purchase #7	$72.89	10.380%	$80.456	$80.46	$80.45	$80.50
7 purchase totals =	$582.13		$628.3286	$628.34	$628.30	$628.50