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	$213.80	7.664%	$230.1856	$230.19	$230.20	$230.20
Purchase #2	$84.32	7.480%	$90.6271	$90.63	$90.65	$90.60
Purchase #3	$65.29	9.570%	$71.5383	$71.54	$71.55	$71.50
Purchase #4	$163.98	3.269%	$169.3405	$169.34	$169.35	$169.30
Purchase #5	$109.49	12.770%	$123.4719	$123.47	$123.45	$123.50
Purchase #6	$146.52	5.365%	$154.3808	$154.38	$154.40	$154.40
Purchase #7	$34.33	8.248%	$37.1615	$37.16	$37.15	$37.20
7 purchase totals =	$817.73		$876.7057	$876.71	$876.75	$876.70