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	$59.41	11.431%	$66.2012	$66.20	$66.20	$66.20
Purchase #2	$62.39	4.585%	$65.2506	$65.25	$65.25	$65.30
Purchase #3	$54.54	13.410%	$61.8538	$61.85	$61.85	$61.90
Purchase #4	$116.33	9.220%	$127.0556	$127.06	$127.05	$127.10
Purchase #5	$83.44	8.452%	$90.4923	$90.49	$90.50	$90.50
Purchase #6	$211.56	5.225%	$222.614	$222.61	$222.60	$222.60
Purchase #7	$206.64	7.835%	$222.8302	$222.83	$222.85	$222.80
7 purchase totals =	$794.31		$856.2977	$856.29	$856.30	$856.40