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	$99.60	5.812%	$105.3888	$105.39	$105.40	$105.40
Purchase #2	$7.81	13.547%	$8.868	$8.87	$8.85	$8.90
Purchase #3	$166.61	11.379%	$185.5686	$185.57	$185.55	$185.60
Purchase #4	$24.71	10.670%	$27.3466	$27.35	$27.35	$27.30
Purchase #5	$69.59	10.691%	$77.0299	$77.03	$77.05	$77.00
Purchase #6	$155.33	10.127%	$171.0603	$171.06	$171.05	$171.10
Purchase #7	$46.66	12.709%	$52.59	$52.59	$52.60	$52.60
7 purchase totals =	$570.31		$627.8522	$627.86	$627.85	$627.90