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	$132.37	5.262%	$139.3353	$139.34	$139.35	$139.30
Purchase #2	$30.87	5.409%	$32.5398	$32.54	$32.55	$32.50
Purchase #3	$152.34	5.174%	$160.2221	$160.22	$160.20	$160.20
Purchase #4	$156.96	3.527%	$162.496	$162.50	$162.50	$162.50
Purchase #5	$184.98	8.499%	$200.7015	$200.70	$200.70	$200.70
Purchase #6	$168.45	4.463%	$175.9679	$175.97	$175.95	$176.00
Purchase #7	$242.37	11.504%	$270.2522	$270.25	$270.25	$270.30
7 purchase totals =	$1,068.34		$1,141.5148	$1,141.52	$1,141.50	$1,141.50