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	$48.54	7.230%	$52.0494	$52.05	$52.05	$52.00
Purchase #2	$127.76	13.626%	$145.1686	$145.17	$145.15	$145.20
Purchase #3	$167.42	11.363%	$186.4439	$186.44	$186.45	$186.40
Purchase #4	$73.33	9.780%	$80.5017	$80.50	$80.50	$80.50
Purchase #5	$111.34	10.509%	$123.0407	$123.04	$123.05	$123.00
Purchase #6	$236.48	10.658%	$261.684	$261.68	$261.70	$261.70
Purchase #7	$63.79	12.512%	$71.7714	$71.77	$71.75	$71.80
7 purchase totals =	$828.66		$920.6597	$920.65	$920.65	$920.60