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	$82.52	8.593%	$89.6109	$89.61	$89.60	$89.60
Purchase #2	$135.72	4.770%	$142.1938	$142.19	$142.20	$142.20
Purchase #3	$189.26	5.572%	$199.8056	$199.81	$199.80	$199.80
Purchase #4	$108.78	9.661%	$119.2892	$119.29	$119.30	$119.30
Purchase #5	$187.27	8.845%	$203.834	$203.83	$203.85	$203.80
Purchase #6	$11.48	12.126%	$12.8721	$12.87	$12.85	$12.90
Purchase #7	$158.93	3.653%	$164.7357	$164.74	$164.75	$164.70
7 purchase totals =	$873.96		$932.3413	$932.34	$932.35	$932.30