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	$151.78	3.334%	$156.8403	$156.84	$156.85	$156.80
Purchase #2	$92.41	5.621%	$97.6044	$97.60	$97.60	$97.60
Purchase #3	$63.96	13.588%	$72.6509	$72.65	$72.65	$72.70
Purchase #4	$20.87	12.760%	$23.533	$23.53	$23.55	$23.50
Purchase #5	$196.58	9.757%	$215.7603	$215.76	$215.75	$215.80
Purchase #6	$54.63	12.393%	$61.4003	$61.40	$61.40	$61.40
Purchase #7	$77.67	9.856%	$85.3252	$85.33	$85.35	$85.30
7 purchase totals =	$657.90		$713.1144	$713.11	$713.15	$713.10