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	$234.71	11.258%	$261.1337	$261.13	$261.15	$261.10
Purchase #2	$85.58	5.232%	$90.0575	$90.06	$90.05	$90.10
Purchase #3	$85.25	3.651%	$88.3625	$88.36	$88.35	$88.40
Purchase #4	$92.27	12.632%	$103.9255	$103.93	$103.95	$103.90
Purchase #5	$187.46	4.680%	$196.2331	$196.23	$196.25	$196.20
Purchase #6	$78.51	12.664%	$88.4525	$88.45	$88.45	$88.50
Purchase #7	$111.65	5.276%	$117.5407	$117.54	$117.55	$117.50
7 purchase totals =	$875.43		$945.7055	$945.70	$945.75	$945.70