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	$153.55	10.372%	$169.4762	$169.48	$169.50	$169.50
Purchase #2	$61.75	3.108%	$63.6692	$63.67	$63.65	$63.70
Purchase #3	$85.72	8.362%	$92.8879	$92.89	$92.90	$92.90
Purchase #4	$108.57	8.142%	$117.4098	$117.41	$117.40	$117.40
Purchase #5	$134.56	10.444%	$148.6134	$148.61	$148.60	$148.60
Purchase #6	$99.72	13.422%	$113.1044	$113.10	$113.10	$113.10
Purchase #7	$150.75	3.720%	$156.3579	$156.36	$156.35	$156.40
7 purchase totals =	$794.62		$861.5188	$861.52	$861.50	$861.60