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	$161.63	4.259%	$168.5138	$168.51	$168.50	$168.50
Purchase #2	$93.41	6.562%	$99.5396	$99.54	$99.55	$99.50
Purchase #3	$128.25	3.174%	$132.3207	$132.32	$132.30	$132.30
Purchase #4	$96.48	12.861%	$108.8883	$108.89	$108.90	$108.90
Purchase #5	$61.66	3.456%	$63.791	$63.79	$63.80	$63.80
Purchase #6	$33.76	10.687%	$37.3679	$37.37	$37.35	$37.40
Purchase #7	$14.41	7.663%	$15.5142	$15.51	$15.50	$15.50
7 purchase totals =	$589.60		$625.9355	$625.93	$625.90	$625.90