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	$121.55	7.175%	$130.2712	$130.27	$130.25	$130.30
Purchase #2	$102.41	8.772%	$111.3934	$111.39	$111.40	$111.40
Purchase #3	$167.69	3.644%	$173.8006	$173.80	$173.80	$173.80
Purchase #4	$184.99	12.790%	$208.6502	$208.65	$208.65	$208.70
Purchase #5	$152.98	13.365%	$173.4258	$173.43	$173.45	$173.40
Purchase #6	$80.47	6.856%	$85.987	$85.99	$86.00	$86.00
Purchase #7	$125.45	6.447%	$133.5378	$133.54	$133.55	$133.50
7 purchase totals =	$935.54		$1,017.0660	$1,017.07	$1,017.10	$1,017.10