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	$233.27	13.357%	$264.4279	$264.43	$264.45	$264.40
Purchase #2	$135.38	4.388%	$141.3205	$141.32	$141.30	$141.30
Purchase #3	$187.44	6.404%	$199.4437	$199.44	$199.45	$199.40
Purchase #4	$24.56	12.207%	$27.558	$27.56	$27.55	$27.60
Purchase #5	$132.46	8.347%	$143.5164	$143.52	$143.50	$143.50
Purchase #6	$241.91	12.818%	$272.918	$272.92	$272.90	$272.90
Purchase #7	$86.28	9.280%	$94.2868	$94.29	$94.30	$94.30
7 purchase totals =	$1,041.30		$1,143.4713	$1,143.48	$1,143.45	$1,143.40