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	$139.59	10.186%	$153.8086	$153.81	$153.80	$153.80
Purchase #2	$203.34	4.422%	$212.3317	$212.33	$212.35	$212.30
Purchase #3	$39.83	7.553%	$42.8384	$42.84	$42.85	$42.80
Purchase #4	$58.83	12.780%	$66.3485	$66.35	$66.35	$66.30
Purchase #5	$140.36	3.534%	$145.3203	$145.32	$145.30	$145.30
Purchase #6	$100.67	8.217%	$108.9421	$108.94	$108.95	$108.90
Purchase #7	$151.28	3.716%	$156.9016	$156.90	$156.90	$156.90
7 purchase totals =	$833.90		$886.4912	$886.49	$886.50	$886.30