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	$47.88	7.682%	$51.5581	$51.56	$51.55	$51.60
Purchase #2	$208.92	3.804%	$216.8673	$216.87	$216.85	$216.90
Purchase #3	$54.62	9.420%	$59.7652	$59.77	$59.75	$59.80
Purchase #4	$41.28	11.852%	$46.1725	$46.17	$46.15	$46.20
Purchase #5	$106.79	12.268%	$119.891	$119.89	$119.90	$119.90
Purchase #6	$229.45	4.107%	$238.8735	$238.87	$238.85	$238.90
Purchase #7	$189.50	5.493%	$199.9092	$199.91	$199.90	$199.90
7 purchase totals =	$878.44		$933.0368	$933.04	$932.95	$933.20