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	$48.37	4.625%	$50.6071	$50.61	$50.60	$50.60
Purchase #2	$49.32	12.214%	$55.3439	$55.34	$55.35	$55.30
Purchase #3	$121.79	4.484%	$127.2511	$127.25	$127.25	$127.30
Purchase #4	$40.71	6.781%	$43.4705	$43.47	$43.45	$43.50
Purchase #5	$201.32	5.188%	$211.7645	$211.76	$211.75	$211.80
Purchase #6	$99.95	9.132%	$109.0774	$109.08	$109.10	$109.10
Purchase #7	$36.30	13.571%	$41.2263	$41.23	$41.25	$41.20
7 purchase totals =	$597.76		$638.7408	$638.74	$638.75	$638.80