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	$21.93	4.572%	$22.9326	$22.93	$22.95	$22.90
Purchase #2	$91.75	10.576%	$101.4535	$101.45	$101.45	$101.50
Purchase #3	$202.25	3.401%	$209.1285	$209.13	$209.15	$209.10
Purchase #4	$13.49	7.139%	$14.4531	$14.45	$14.45	$14.50
Purchase #5	$113.36	4.399%	$118.3467	$118.35	$118.35	$118.30
Purchase #6	$104.51	4.525%	$109.2391	$109.24	$109.25	$109.20
Purchase #7	$89.86	12.208%	$100.8301	$100.83	$100.85	$100.80
7 purchase totals =	$637.15		$676.3836	$676.38	$676.45	$676.30