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	$66.40	8.558%	$72.0825	$72.08	$72.10	$72.10
Purchase #2	$162.42	10.427%	$179.3555	$179.36	$179.35	$179.40
Purchase #3	$76.30	5.743%	$80.6819	$80.68	$80.70	$80.70
Purchase #4	$235.65	7.593%	$253.5429	$253.54	$253.55	$253.50
Purchase #5	$11.47	3.131%	$11.8291	$11.83	$11.85	$11.80
Purchase #6	$201.83	11.604%	$225.2504	$225.25	$225.25	$225.30
Purchase #7	$173.76	13.184%	$196.6685	$196.67	$196.65	$196.70
7 purchase totals =	$927.83		$1,019.4108	$1,019.41	$1,019.45	$1,019.50