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	$90.33	5.376%	$95.1861	$95.19	$95.20	$95.20
Purchase #2	$63.38	9.848%	$69.6217	$69.62	$69.60	$69.60
Purchase #3	$56.54	12.705%	$63.7234	$63.72	$63.70	$63.70
Purchase #4	$79.37	7.810%	$85.5688	$85.57	$85.55	$85.60
Purchase #5	$204.63	8.619%	$222.2671	$222.27	$222.25	$222.30
Purchase #6	$211.32	9.572%	$231.5476	$231.55	$231.55	$231.50
Purchase #7	$19.57	10.796%	$21.6828	$21.68	$21.70	$21.70
7 purchase totals =	$725.14		$789.5975	$789.60	$789.55	$789.60