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	$90.43	5.744%	$95.6243	$95.62	$95.60	$95.60
Purchase #2	$153.69	4.245%	$160.2141	$160.21	$160.20	$160.20
Purchase #3	$11.56	3.166%	$11.926	$11.93	$11.95	$11.90
Purchase #4	$174.95	12.245%	$196.3726	$196.37	$196.35	$196.40
Purchase #5	$66.33	9.296%	$72.496	$72.50	$72.50	$72.50
Purchase #6	$154.47	13.649%	$175.5536	$175.55	$175.55	$175.60
Purchase #7	$174.63	11.564%	$194.8242	$194.82	$194.80	$194.80
7 purchase totals =	$826.06		$907.0108	$907.00	$906.95	$907.00