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	$210.59	4.161%	$219.3526	$219.35	$219.35	$219.40
Purchase #2	$36.63	9.824%	$40.2285	$40.23	$40.25	$40.20
Purchase #3	$180.58	10.281%	$199.1454	$199.15	$199.15	$199.10
Purchase #4	$213.90	5.105%	$224.8196	$224.82	$224.80	$224.80
Purchase #5	$142.91	9.181%	$156.0306	$156.03	$156.05	$156.00
Purchase #6	$89.55	8.156%	$96.8537	$96.85	$96.85	$96.90
Purchase #7	$178.38	5.633%	$188.4281	$188.43	$188.45	$188.40
7 purchase totals =	$1,052.54		$1,124.8585	$1,124.86	$1,124.90	$1,124.80