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	$242.81	9.129%	$264.9761	$264.98	$265.00	$265.00
Purchase #2	$19.85	6.214%	$21.0835	$21.08	$21.10	$21.10
Purchase #3	$71.78	4.665%	$75.1285	$75.13	$75.15	$75.10
Purchase #4	$219.37	4.204%	$228.5923	$228.59	$228.60	$228.60
Purchase #5	$37.92	6.798%	$40.4978	$40.50	$40.50	$40.50
Purchase #6	$222.27	10.598%	$245.8262	$245.83	$245.85	$245.80
Purchase #7	$173.91	12.624%	$195.8644	$195.86	$195.85	$195.90
7 purchase totals =	$987.91		$1,071.9688	$1,071.97	$1,072.05	$1,072.00