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	$30.88	8.825%	$33.6052	$33.61	$33.60	$33.60
Purchase #2	$59.59	8.153%	$64.4484	$64.45	$64.45	$64.40
Purchase #3	$95.82	10.163%	$105.5582	$105.56	$105.55	$105.60
Purchase #4	$127.69	4.554%	$133.505	$133.51	$133.50	$133.50
Purchase #5	$134.36	10.718%	$148.7607	$148.76	$148.75	$148.80
Purchase #6	$25.55	11.782%	$28.5603	$28.56	$28.55	$28.60
Purchase #7	$214.43	12.404%	$241.0279	$241.03	$241.05	$241.00
7 purchase totals =	$688.32		$755.4657	$755.48	$755.45	$755.50