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	$87.60	3.411%	$90.588	$90.59	$90.60	$90.60
Purchase #2	$79.30	12.672%	$89.3489	$89.35	$89.35	$89.30
Purchase #3	$101.85	3.467%	$105.3811	$105.38	$105.40	$105.40
Purchase #4	$234.63	7.357%	$251.8917	$251.89	$251.90	$251.90
Purchase #5	$125.49	5.166%	$131.9728	$131.97	$131.95	$132.00
Purchase #6	$106.83	9.407%	$116.8795	$116.88	$116.90	$116.90
Purchase #7	$219.57	6.776%	$234.4481	$234.45	$234.45	$234.40
7 purchase totals =	$955.27		$1,020.5101	$1,020.51	$1,020.55	$1,020.50