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	$52.45	3.440%	$54.2543	$54.25	$54.25	$54.30
Purchase #2	$25.56	5.817%	$27.0468	$27.05	$27.05	$27.00
Purchase #3	$202.58	12.119%	$227.1307	$227.13	$227.15	$227.10
Purchase #4	$61.86	4.359%	$64.5565	$64.56	$64.55	$64.60
Purchase #5	$132.71	7.575%	$142.7628	$142.76	$142.75	$142.80
Purchase #6	$11.39	13.234%	$12.8974	$12.90	$12.90	$12.90
Purchase #7	$176.72	10.378%	$195.06	$195.06	$195.05	$195.10
7 purchase totals =	$663.27		$723.7085	$723.71	$723.70	$723.80