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	$51.81	3.385%	$53.5638	$53.56	$53.55	$53.60
Purchase #2	$185.79	6.396%	$197.6731	$197.67	$197.65	$197.70
Purchase #3	$93.88	3.424%	$97.0945	$97.09	$97.10	$97.10
Purchase #4	$184.73	8.522%	$200.4727	$200.47	$200.45	$200.50
Purchase #5	$80.51	3.167%	$83.0598	$83.06	$83.05	$83.10
Purchase #6	$17.54	3.425%	$18.1407	$18.14	$18.15	$18.10
Purchase #7	$175.42	5.663%	$185.354	$185.35	$185.35	$185.40
7 purchase totals =	$789.68		$835.3586	$835.34	$835.30	$835.50