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	$150.88	4.856%	$158.2067	$158.21	$158.20	$158.20
Purchase #2	$49.94	4.812%	$52.3431	$52.34	$52.35	$52.30
Purchase #3	$195.83	7.665%	$210.8404	$210.84	$210.85	$210.80
Purchase #4	$199.66	9.663%	$218.9531	$218.95	$218.95	$219.00
Purchase #5	$83.95	7.870%	$90.5569	$90.56	$90.55	$90.60
Purchase #6	$55.30	3.388%	$57.1736	$57.17	$57.15	$57.20
Purchase #7	$102.94	13.511%	$116.8482	$116.85	$116.85	$116.80
7 purchase totals =	$838.50		$904.9220	$904.92	$904.90	$904.90