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	$186.33	7.676%	$200.6327	$200.63	$200.65	$200.60
Purchase #2	$105.37	3.762%	$109.334	$109.33	$109.35	$109.30
Purchase #3	$18.93	5.748%	$20.0181	$20.02	$20.00	$20.00
Purchase #4	$28.45	8.526%	$30.8756	$30.88	$30.90	$30.90
Purchase #5	$167.88	3.545%	$173.8313	$173.83	$173.85	$173.80
Purchase #6	$234.72	8.699%	$255.1383	$255.14	$255.15	$255.10
Purchase #7	$19.96	5.476%	$21.053	$21.05	$21.05	$21.10
7 purchase totals =	$761.64		$810.8830	$810.88	$810.95	$810.80