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	$152.31	9.414%	$166.6485	$166.65	$166.65	$166.60
Purchase #2	$38.96	12.578%	$43.8604	$43.86	$43.85	$43.90
Purchase #3	$68.82	10.283%	$75.8968	$75.90	$75.90	$75.90
Purchase #4	$170.88	4.574%	$178.6961	$178.70	$178.70	$178.70
Purchase #5	$177.78	7.414%	$190.9606	$190.96	$190.95	$191.00
Purchase #6	$105.98	5.279%	$111.5747	$111.57	$111.55	$111.60
Purchase #7	$114.70	13.568%	$130.2625	$130.26	$130.25	$130.30
7 purchase totals =	$829.43		$897.8996	$897.90	$897.85	$898.00