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	$205.29	4.398%	$214.3187	$214.32	$214.30	$214.30
Purchase #2	$99.92	5.330%	$105.2457	$105.25	$105.25	$105.20
Purchase #3	$168.45	8.154%	$182.1854	$182.19	$182.20	$182.20
Purchase #4	$143.89	12.206%	$161.4532	$161.45	$161.45	$161.50
Purchase #5	$104.72	9.221%	$114.3762	$114.38	$114.40	$114.40
Purchase #6	$248.89	10.467%	$274.9413	$274.94	$274.95	$274.90
Purchase #7	$179.92	6.610%	$191.8127	$191.81	$191.80	$191.80
7 purchase totals =	$1,151.08		$1,244.3332	$1,244.34	$1,244.35	$1,244.30