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	$206.43	7.346%	$221.5943	$221.59	$221.60	$221.60
Purchase #2	$205.32	6.676%	$219.0272	$219.03	$219.05	$219.00
Purchase #3	$246.49	9.426%	$269.7241	$269.72	$269.70	$269.70
Purchase #4	$119.79	3.416%	$123.882	$123.88	$123.90	$123.90
Purchase #5	$218.65	5.163%	$229.9389	$229.94	$229.95	$229.90
Purchase #6	$70.80	13.428%	$80.307	$80.31	$80.30	$80.30
Purchase #7	$100.87	10.162%	$111.1204	$111.12	$111.10	$111.10
7 purchase totals =	$1,168.35		$1,255.5939	$1,255.59	$1,255.60	$1,255.50