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	$179.46	3.133%	$185.0825	$185.08	$185.10	$185.10
Purchase #2	$33.81	6.696%	$36.0739	$36.07	$36.05	$36.10
Purchase #3	$143.60	7.523%	$154.403	$154.40	$154.40	$154.40
Purchase #4	$124.54	7.355%	$133.6999	$133.70	$133.70	$133.70
Purchase #5	$152.56	7.772%	$164.417	$164.42	$164.40	$164.40
Purchase #6	$240.37	7.536%	$258.4843	$258.48	$258.50	$258.50
Purchase #7	$119.90	9.548%	$131.3481	$131.35	$131.35	$131.30
7 purchase totals =	$994.24		$1,063.5087	$1,063.50	$1,063.50	$1,063.50