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	$153.30	10.797%	$169.8518	$169.85	$169.85	$169.90
Purchase #2	$233.88	7.685%	$251.8537	$251.85	$251.85	$251.90
Purchase #3	$69.85	10.870%	$77.4427	$77.44	$77.45	$77.40
Purchase #4	$129.70	12.776%	$146.2705	$146.27	$146.25	$146.30
Purchase #5	$10.46	8.113%	$11.3086	$11.31	$11.30	$11.30
Purchase #6	$87.75	12.625%	$98.8284	$98.83	$98.85	$98.80
Purchase #7	$123.83	6.204%	$131.5124	$131.51	$131.50	$131.50
7 purchase totals =	$808.77		$887.0681	$887.06	$887.05	$887.10