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	$243.49	7.260%	$261.1674	$261.17	$261.15	$261.20
Purchase #2	$41.67	11.832%	$46.6004	$46.60	$46.60	$46.60
Purchase #3	$51.69	5.149%	$54.3515	$54.35	$54.35	$54.40
Purchase #4	$126.35	3.289%	$130.5057	$130.51	$130.50	$130.50
Purchase #5	$142.80	12.494%	$160.6414	$160.64	$160.65	$160.60
Purchase #6	$178.80	3.119%	$184.3768	$184.38	$184.40	$184.40
Purchase #7	$95.50	10.862%	$105.8732	$105.87	$105.85	$105.90
7 purchase totals =	$880.30		$943.5164	$943.52	$943.50	$943.60