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	$140.96	5.199%	$148.2885	$148.29	$148.30	$148.30
Purchase #2	$203.45	6.352%	$216.3731	$216.37	$216.35	$216.40
Purchase #3	$43.75	3.244%	$45.1693	$45.17	$45.15	$45.20
Purchase #4	$31.32	9.500%	$34.2954	$34.30	$34.30	$34.30
Purchase #5	$208.38	4.723%	$218.2218	$218.22	$218.20	$218.20
Purchase #6	$65.93	9.584%	$72.2487	$72.25	$72.25	$72.20
Purchase #7	$38.93	8.353%	$42.1818	$42.18	$42.20	$42.20
7 purchase totals =	$732.72		$776.7786	$776.78	$776.75	$776.80