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	$37.30	13.528%	$42.3459	$42.35	$42.35	$42.30
Purchase #2	$94.29	10.866%	$104.5356	$104.54	$104.55	$104.50
Purchase #3	$118.69	11.716%	$132.5957	$132.60	$132.60	$132.60
Purchase #4	$138.86	6.113%	$147.3485	$147.35	$147.35	$147.30
Purchase #5	$225.72	8.844%	$245.6827	$245.68	$245.70	$245.70
Purchase #6	$199.85	11.309%	$222.451	$222.45	$222.45	$222.50
Purchase #7	$145.76	9.351%	$159.39	$159.39	$159.40	$159.40
7 purchase totals =	$960.47		$1,054.3494	$1,054.36	$1,054.40	$1,054.30