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	$47.82	8.870%	$52.0616	$52.06	$52.05	$52.10
Purchase #2	$75.28	9.521%	$82.4474	$82.45	$82.45	$82.40
Purchase #3	$69.34	4.286%	$72.3119	$72.31	$72.30	$72.30
Purchase #4	$30.47	5.518%	$32.1513	$32.15	$32.15	$32.20
Purchase #5	$133.83	7.534%	$143.9128	$143.91	$143.90	$143.90
Purchase #6	$63.82	11.696%	$71.2844	$71.28	$71.30	$71.30
Purchase #7	$180.88	5.532%	$190.8863	$190.89	$190.90	$190.90
7 purchase totals =	$601.44		$645.0557	$645.05	$645.05	$645.10