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	$246.69	11.404%	$274.8225	$274.82	$274.80	$274.80
Purchase #2	$48.84	13.229%	$55.301	$55.30	$55.30	$55.30
Purchase #3	$55.77	8.570%	$60.5495	$60.55	$60.55	$60.50
Purchase #4	$210.82	9.674%	$231.2147	$231.21	$231.20	$231.20
Purchase #5	$176.41	11.144%	$196.0691	$196.07	$196.05	$196.10
Purchase #6	$11.52	11.775%	$12.8765	$12.88	$12.90	$12.90
Purchase #7	$105.63	10.230%	$116.4359	$116.44	$116.45	$116.40
7 purchase totals =	$855.68		$947.2692	$947.27	$947.25	$947.20