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	$155.29	9.286%	$169.7102	$169.71	$169.70	$169.70
Purchase #2	$80.82	12.386%	$90.8304	$90.83	$90.85	$90.80
Purchase #3	$195.54	5.523%	$206.3397	$206.34	$206.35	$206.30
Purchase #4	$80.68	7.333%	$86.5963	$86.60	$86.60	$86.60
Purchase #5	$225.84	4.226%	$235.384	$235.38	$235.40	$235.40
Purchase #6	$61.43	9.457%	$67.2394	$67.24	$67.25	$67.20
Purchase #7	$143.47	12.514%	$161.4238	$161.42	$161.40	$161.40
7 purchase totals =	$943.07		$1,017.5238	$1,017.52	$1,017.55	$1,017.40