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	$164.72	10.298%	$181.6829	$181.68	$181.70	$181.70
Purchase #2	$240.79	8.628%	$261.5654	$261.57	$261.55	$261.60
Purchase #3	$173.36	8.641%	$188.34	$188.34	$188.35	$188.30
Purchase #4	$11.49	8.620%	$12.4804	$12.48	$12.50	$12.50
Purchase #5	$33.75	9.766%	$37.046	$37.05	$37.05	$37.00
Purchase #6	$27.70	5.610%	$29.254	$29.25	$29.25	$29.30
Purchase #7	$132.50	3.743%	$137.4595	$137.46	$137.45	$137.50
7 purchase totals =	$784.31		$847.8282	$847.83	$847.85	$847.90