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	$64.80	4.251%	$67.5546	$67.55	$67.55	$67.60
Purchase #2	$43.92	6.599%	$46.8183	$46.82	$46.80	$46.80
Purchase #3	$109.25	6.864%	$116.7489	$116.75	$116.75	$116.70
Purchase #4	$93.85	3.456%	$97.0935	$97.09	$97.10	$97.10
Purchase #5	$238.54	6.160%	$253.2341	$253.23	$253.25	$253.20
Purchase #6	$41.35	12.613%	$46.5655	$46.57	$46.55	$46.60
Purchase #7	$142.59	5.576%	$150.5408	$150.54	$150.55	$150.50
7 purchase totals =	$734.30		$778.5557	$778.55	$778.55	$778.50