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	$143.85	5.257%	$151.4122	$151.41	$151.40	$151.40
Purchase #2	$169.97	7.449%	$182.6311	$182.63	$182.65	$182.60
Purchase #3	$124.69	7.409%	$133.9283	$133.93	$133.95	$133.90
Purchase #4	$160.34	11.754%	$179.1864	$179.19	$179.20	$179.20
Purchase #5	$112.25	13.697%	$127.6249	$127.62	$127.60	$127.60
Purchase #6	$59.64	7.224%	$63.9484	$63.95	$63.95	$63.90
Purchase #7	$52.65	13.612%	$59.8167	$59.82	$59.80	$59.80
7 purchase totals =	$823.39		$898.5480	$898.55	$898.55	$898.40