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	$62.85	6.295%	$66.8064	$66.81	$66.80	$66.80
Purchase #2	$206.79	10.376%	$228.2465	$228.25	$228.25	$228.20
Purchase #3	$39.51	10.486%	$43.653	$43.65	$43.65	$43.70
Purchase #4	$171.70	6.801%	$183.3773	$183.38	$183.40	$183.40
Purchase #5	$98.35	10.189%	$108.3709	$108.37	$108.35	$108.40
Purchase #6	$37.76	7.761%	$40.6906	$40.69	$40.70	$40.70
Purchase #7	$74.95	4.818%	$78.5611	$78.56	$78.55	$78.60
7 purchase totals =	$691.91		$749.7058	$749.71	$749.70	$749.80