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	$101.27	11.424%	$112.8391	$112.84	$112.85	$112.80
Purchase #2	$182.29	4.578%	$190.6352	$190.64	$190.65	$190.60
Purchase #3	$47.43	8.698%	$51.5555	$51.56	$51.55	$51.60
Purchase #4	$195.77	13.529%	$222.2557	$222.26	$222.25	$222.30
Purchase #5	$40.98	10.859%	$45.43	$45.43	$45.45	$45.40
Purchase #6	$173.80	9.711%	$190.6777	$190.68	$190.70	$190.70
Purchase #7	$246.43	6.866%	$263.3499	$263.35	$263.35	$263.30
7 purchase totals =	$987.97		$1,076.7431	$1,076.76	$1,076.80	$1,076.70