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	$45.56	8.557%	$49.4586	$49.46	$49.45	$49.50
Purchase #2	$15.38	13.572%	$17.4674	$17.47	$17.45	$17.50
Purchase #3	$166.39	11.636%	$185.7511	$185.75	$185.75	$185.80
Purchase #4	$61.89	5.224%	$65.1231	$65.12	$65.10	$65.10
Purchase #5	$48.61	9.740%	$53.3446	$53.34	$53.35	$53.30
Purchase #6	$55.64	7.712%	$59.931	$59.93	$59.95	$59.90
Purchase #7	$117.81	8.105%	$127.3585	$127.36	$127.35	$127.40
7 purchase totals =	$511.28		$558.4343	$558.43	$558.40	$558.50