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	$184.90	11.524%	$206.2079	$206.21	$206.20	$206.20
Purchase #2	$12.73	5.656%	$13.45	$13.45	$13.45	$13.50
Purchase #3	$242.45	13.265%	$274.611	$274.61	$274.60	$274.60
Purchase #4	$234.52	13.290%	$265.6877	$265.69	$265.70	$265.70
Purchase #5	$100.56	7.824%	$108.4278	$108.43	$108.45	$108.40
Purchase #6	$49.37	5.566%	$52.1179	$52.12	$52.10	$52.10
Purchase #7	$100.78	10.547%	$111.4093	$111.41	$111.40	$111.40
7 purchase totals =	$925.31		$1,031.9116	$1,031.92	$1,031.90	$1,031.90