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	$56.59	9.181%	$61.7855	$61.79	$61.80	$61.80
Purchase #2	$138.39	10.412%	$152.7992	$152.80	$152.80	$152.80
Purchase #3	$142.43	7.803%	$153.5438	$153.54	$153.55	$153.50
Purchase #4	$134.41	11.789%	$150.2556	$150.26	$150.25	$150.30
Purchase #5	$50.77	11.809%	$56.7654	$56.77	$56.75	$56.80
Purchase #6	$133.63	11.118%	$148.487	$148.49	$148.50	$148.50
Purchase #7	$97.61	10.872%	$108.2222	$108.22	$108.20	$108.20
7 purchase totals =	$753.83		$831.8587	$831.87	$831.85	$831.90