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	$106.85	4.124%	$111.2565	$111.26	$111.25	$111.30
Purchase #2	$55.59	7.218%	$59.6025	$59.60	$59.60	$59.60
Purchase #3	$98.26	5.481%	$103.6456	$103.65	$103.65	$103.60
Purchase #4	$141.38	7.424%	$151.8761	$151.88	$151.90	$151.90
Purchase #5	$155.74	8.605%	$169.1414	$169.14	$169.15	$169.10
Purchase #6	$40.65	6.857%	$43.4374	$43.44	$43.45	$43.40
Purchase #7	$112.42	12.620%	$126.6074	$126.61	$126.60	$126.60
7 purchase totals =	$710.89		$765.5669	$765.58	$765.60	$765.50