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	$33.42	3.601%	$34.6235	$34.62	$34.60	$34.60
Purchase #2	$76.89	3.340%	$79.4581	$79.46	$79.45	$79.50
Purchase #3	$56.83	8.382%	$61.5935	$61.59	$61.60	$61.60
Purchase #4	$164.27	12.492%	$184.7906	$184.79	$184.80	$184.80
Purchase #5	$214.96	3.469%	$222.417	$222.42	$222.40	$222.40
Purchase #6	$83.54	13.358%	$94.6993	$94.70	$94.70	$94.70
Purchase #7	$100.44	10.367%	$110.8526	$110.85	$110.85	$110.90
7 purchase totals =	$730.35		$788.4346	$788.43	$788.40	$788.50