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	$91.38	6.585%	$97.3974	$97.40	$97.40	$97.40
Purchase #2	$70.37	4.366%	$73.4424	$73.44	$73.45	$73.40
Purchase #3	$40.91	3.495%	$42.3398	$42.34	$42.35	$42.30
Purchase #4	$108.52	13.670%	$123.3547	$123.35	$123.35	$123.40
Purchase #5	$157.87	12.514%	$177.6259	$177.63	$177.65	$177.60
Purchase #6	$55.75	11.241%	$62.0169	$62.02	$62.00	$62.00
Purchase #7	$115.54	7.188%	$123.845	$123.85	$123.85	$123.80
7 purchase totals =	$640.34		$700.0221	$700.03	$700.05	$699.90