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	$243.83	6.874%	$260.5909	$260.59	$260.60	$260.60
Purchase #2	$62.41	13.314%	$70.7193	$70.72	$70.70	$70.70
Purchase #3	$14.27	5.815%	$15.0998	$15.10	$15.10	$15.10
Purchase #4	$238.98	4.640%	$250.0687	$250.07	$250.05	$250.10
Purchase #5	$105.29	10.215%	$116.0454	$116.05	$116.05	$116.00
Purchase #6	$65.33	12.127%	$73.2526	$73.25	$73.25	$73.30
Purchase #7	$167.81	13.481%	$190.4325	$190.43	$190.45	$190.40
7 purchase totals =	$897.92		$976.2092	$976.21	$976.20	$976.20