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	$50.55	11.287%	$56.2556	$56.26	$56.25	$56.30
Purchase #2	$199.67	8.455%	$216.5521	$216.55	$216.55	$216.60
Purchase #3	$91.53	9.399%	$100.1329	$100.13	$100.15	$100.10
Purchase #4	$221.86	3.643%	$229.9424	$229.94	$229.95	$229.90
Purchase #5	$20.26	11.645%	$22.6193	$22.62	$22.60	$22.60
Purchase #6	$223.83	9.855%	$245.8884	$245.89	$245.90	$245.90
Purchase #7	$197.86	3.803%	$205.3846	$205.38	$205.40	$205.40
7 purchase totals =	$1,005.56		$1,076.7753	$1,076.77	$1,076.80	$1,076.80