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	$68.51	4.665%	$71.706	$71.71	$71.70	$71.70
Purchase #2	$178.35	10.412%	$196.9198	$196.92	$196.90	$196.90
Purchase #3	$42.67	7.334%	$45.7994	$45.80	$45.80	$45.80
Purchase #4	$221.73	10.508%	$245.0294	$245.03	$245.05	$245.00
Purchase #5	$104.96	3.720%	$108.8645	$108.86	$108.85	$108.90
Purchase #6	$122.50	8.464%	$132.8684	$132.87	$132.85	$132.90
Purchase #7	$68.78	4.609%	$71.9501	$71.95	$71.95	$72.00
7 purchase totals =	$807.50		$873.1376	$873.14	$873.10	$873.20