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	$74.47	4.791%	$78.0379	$78.04	$78.05	$78.00
Purchase #2	$217.78	10.419%	$240.4705	$240.47	$240.45	$240.50
Purchase #3	$106.83	9.475%	$116.9521	$116.95	$116.95	$117.00
Purchase #4	$41.55	8.696%	$45.1632	$45.16	$45.15	$45.20
Purchase #5	$62.42	13.419%	$70.7961	$70.80	$70.80	$70.80
Purchase #6	$129.74	3.118%	$133.7853	$133.79	$133.80	$133.80
Purchase #7	$241.74	5.835%	$255.8455	$255.85	$255.85	$255.80
7 purchase totals =	$874.53		$941.0506	$941.06	$941.05	$941.10