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	$85.72	10.161%	$94.43	$94.43	$94.45	$94.40
Purchase #2	$9.70	5.755%	$10.2582	$10.26	$10.25	$10.30
Purchase #3	$197.77	13.698%	$224.8605	$224.86	$224.85	$224.90
Purchase #4	$133.79	6.336%	$142.2669	$142.27	$142.25	$142.30
Purchase #5	$132.67	9.735%	$145.5854	$145.59	$145.60	$145.60
Purchase #6	$215.49	3.807%	$223.6937	$223.69	$223.70	$223.70
Purchase #7	$86.91	9.645%	$95.2925	$95.29	$95.30	$95.30
7 purchase totals =	$862.05		$936.3872	$936.39	$936.40	$936.50