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	$100.91	10.553%	$111.559	$111.56	$111.55	$111.60
Purchase #2	$111.36	11.184%	$123.8145	$123.81	$123.80	$123.80
Purchase #3	$102.54	10.572%	$113.3805	$113.38	$113.40	$113.40
Purchase #4	$115.58	6.555%	$123.1563	$123.16	$123.15	$123.20
Purchase #5	$199.59	12.583%	$224.7044	$224.70	$224.70	$224.70
Purchase #6	$73.30	5.704%	$77.481	$77.48	$77.50	$77.50
Purchase #7	$80.75	10.435%	$89.1763	$89.18	$89.20	$89.20
7 purchase totals =	$784.03		$863.2720	$863.27	$863.30	$863.40