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	$5.36	5.622%	$5.6613	$5.66	$5.65	$5.70
Purchase #2	$93.43	6.396%	$99.4058	$99.41	$99.40	$99.40
Purchase #3	$143.86	4.520%	$150.3625	$150.36	$150.35	$150.40
Purchase #4	$150.25	5.196%	$158.057	$158.06	$158.05	$158.10
Purchase #5	$20.34	7.762%	$21.9188	$21.92	$21.90	$21.90
Purchase #6	$78.98	5.167%	$83.0609	$83.06	$83.05	$83.10
Purchase #7	$47.78	13.139%	$54.0578	$54.06	$54.05	$54.10
7 purchase totals =	$540.00		$572.5241	$572.53	$572.45	$572.70