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	$117.52	6.228%	$124.8391	$124.84	$124.85	$124.80
Purchase #2	$148.58	9.278%	$162.3653	$162.37	$162.35	$162.40
Purchase #3	$220.84	10.257%	$243.4916	$243.49	$243.50	$243.50
Purchase #4	$124.47	3.476%	$128.7966	$128.80	$128.80	$128.80
Purchase #5	$78.49	4.810%	$82.2654	$82.27	$82.25	$82.30
Purchase #6	$7.48	5.139%	$7.8644	$7.86	$7.85	$7.90
Purchase #7	$215.77	4.247%	$224.9338	$224.93	$224.95	$224.90
7 purchase totals =	$913.15		$974.5562	$974.56	$974.55	$974.60