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	$158.45	6.549%	$168.8269	$168.83	$168.85	$168.80
Purchase #2	$45.33	6.697%	$48.3658	$48.37	$48.35	$48.40
Purchase #3	$61.53	5.798%	$65.0975	$65.10	$65.10	$65.10
Purchase #4	$52.64	4.639%	$55.082	$55.08	$55.10	$55.10
Purchase #5	$114.58	11.398%	$127.6398	$127.64	$127.65	$127.60
Purchase #6	$228.96	6.328%	$243.4486	$243.45	$243.45	$243.40
Purchase #7	$238.90	11.153%	$265.5445	$265.54	$265.55	$265.50
7 purchase totals =	$900.39		$974.0051	$974.01	$974.05	$973.90