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	$68.39	6.250%	$72.6644	$72.66	$72.65	$72.70
Purchase #2	$17.40	5.452%	$18.3486	$18.35	$18.35	$18.30
Purchase #3	$24.34	7.295%	$26.1156	$26.12	$26.10	$26.10
Purchase #4	$73.95	13.493%	$83.9281	$83.93	$83.95	$83.90
Purchase #5	$152.42	10.759%	$168.8189	$168.82	$168.80	$168.80
Purchase #6	$97.83	12.357%	$109.9189	$109.92	$109.90	$109.90
Purchase #7	$32.45	12.815%	$36.6085	$36.61	$36.60	$36.60
7 purchase totals =	$466.78		$516.4030	$516.41	$516.35	$516.30