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	$158.48	12.363%	$178.0729	$178.07	$178.05	$178.10
Purchase #2	$222.37	12.207%	$249.5147	$249.51	$249.50	$249.50
Purchase #3	$96.80	12.102%	$108.5147	$108.51	$108.50	$108.50
Purchase #4	$58.75	10.380%	$64.8483	$64.85	$64.85	$64.80
Purchase #5	$177.79	12.502%	$200.0173	$200.02	$200.00	$200.00
Purchase #6	$60.72	5.173%	$63.861	$63.86	$63.85	$63.90
Purchase #7	$80.52	11.106%	$89.4626	$89.46	$89.45	$89.50
7 purchase totals =	$855.43		$954.2915	$954.28	$954.20	$954.30