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	$244.53	13.221%	$276.8593	$276.86	$276.85	$276.90
Purchase #2	$75.49	11.657%	$84.2899	$84.29	$84.30	$84.30
Purchase #3	$155.93	6.361%	$165.8487	$165.85	$165.85	$165.80
Purchase #4	$193.57	3.659%	$200.6527	$200.65	$200.65	$200.70
Purchase #5	$248.45	4.419%	$259.429	$259.43	$259.45	$259.40
Purchase #6	$51.40	5.687%	$54.3231	$54.32	$54.30	$54.30
Purchase #7	$105.52	8.440%	$114.4259	$114.43	$114.45	$114.40
7 purchase totals =	$1,074.89		$1,155.8286	$1,155.83	$1,155.85	$1,155.80