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	$7.30	3.658%	$7.567	$7.57	$7.55	$7.60
Purchase #2	$77.69	13.792%	$88.405	$88.41	$88.40	$88.40
Purchase #3	$177.92	5.237%	$187.2377	$187.24	$187.25	$187.20
Purchase #4	$161.75	10.671%	$179.0103	$179.01	$179.00	$179.00
Purchase #5	$82.43	13.296%	$93.3899	$93.39	$93.40	$93.40
Purchase #6	$73.25	6.730%	$78.1797	$78.18	$78.20	$78.20
Purchase #7	$81.29	4.707%	$85.1163	$85.12	$85.10	$85.10
7 purchase totals =	$661.63		$718.9059	$718.92	$718.90	$718.90