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	$102.93	6.763%	$109.8912	$109.89	$109.90	$109.90
Purchase #2	$211.95	6.422%	$225.5614	$225.56	$225.55	$225.60
Purchase #3	$63.72	3.670%	$66.0585	$66.06	$66.05	$66.10
Purchase #4	$109.82	7.391%	$117.9368	$117.94	$117.95	$117.90
Purchase #5	$78.26	7.128%	$83.8384	$83.84	$83.85	$83.80
Purchase #6	$194.31	13.681%	$220.8936	$220.89	$220.90	$220.90
Purchase #7	$21.83	10.217%	$24.0604	$24.06	$24.05	$24.10
7 purchase totals =	$782.82		$848.2403	$848.24	$848.25	$848.30