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	$177.43	10.646%	$196.3192	$196.32	$196.30	$196.30
Purchase #2	$13.57	4.469%	$14.1764	$14.18	$14.20	$14.20
Purchase #3	$50.52	5.665%	$53.382	$53.38	$53.40	$53.40
Purchase #4	$171.97	9.822%	$188.8609	$188.86	$188.85	$188.90
Purchase #5	$149.27	12.593%	$168.0676	$168.07	$168.05	$168.10
Purchase #6	$211.52	5.323%	$222.7792	$222.78	$222.80	$222.80
Purchase #7	$67.73	10.717%	$74.9886	$74.99	$75.00	$75.00
7 purchase totals =	$842.01		$918.5739	$918.58	$918.60	$918.70