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	$219.67	8.774%	$238.9438	$238.94	$238.95	$238.90
Purchase #2	$122.64	13.806%	$139.5717	$139.57	$139.55	$139.60
Purchase #3	$29.83	9.406%	$32.6358	$32.64	$32.65	$32.60
Purchase #4	$28.53	9.412%	$31.2152	$31.22	$31.20	$31.20
Purchase #5	$46.29	11.348%	$51.543	$51.54	$51.55	$51.50
Purchase #6	$199.96	7.471%	$214.899	$214.90	$214.90	$214.90
Purchase #7	$71.75	7.803%	$77.3487	$77.35	$77.35	$77.30
7 purchase totals =	$718.67		$786.1572	$786.16	$786.15	$786.00