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	$130.94	10.325%	$144.4596	$144.46	$144.45	$144.50
Purchase #2	$142.60	9.687%	$156.4137	$156.41	$156.40	$156.40
Purchase #3	$39.72	5.301%	$41.8256	$41.83	$41.85	$41.80
Purchase #4	$150.74	12.408%	$169.4438	$169.44	$169.45	$169.40
Purchase #5	$108.72	5.187%	$114.3593	$114.36	$114.35	$114.40
Purchase #6	$250.46	11.316%	$278.8021	$278.80	$278.80	$278.80
Purchase #7	$231.34	3.438%	$239.2935	$239.29	$239.30	$239.30
7 purchase totals =	$1,054.52		$1,144.5976	$1,144.59	$1,144.60	$1,144.60