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	$192.31	10.128%	$211.7872	$211.79	$211.80	$211.80
Purchase #2	$77.43	10.782%	$85.7785	$85.78	$85.80	$85.80
Purchase #3	$246.69	9.644%	$270.4808	$270.48	$270.50	$270.50
Purchase #4	$228.43	12.848%	$257.7787	$257.78	$257.80	$257.80
Purchase #5	$67.87	6.778%	$72.4702	$72.47	$72.45	$72.50
Purchase #6	$44.82	11.749%	$50.0859	$50.09	$50.10	$50.10
Purchase #7	$53.45	6.835%	$57.1033	$57.10	$57.10	$57.10
7 purchase totals =	$911.00		$1,005.4846	$1,005.49	$1,005.55	$1,005.60