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	$243.63	5.418%	$256.8299	$256.83	$256.85	$256.80
Purchase #2	$9.45	4.245%	$9.8512	$9.85	$9.85	$9.90
Purchase #3	$224.49	11.219%	$249.6755	$249.68	$249.70	$249.70
Purchase #4	$215.32	11.668%	$240.4435	$240.44	$240.45	$240.40
Purchase #5	$54.93	8.479%	$59.5875	$59.59	$59.60	$59.60
Purchase #6	$169.45	12.209%	$190.1382	$190.14	$190.15	$190.10
Purchase #7	$169.76	9.449%	$185.8006	$185.80	$185.80	$185.80
7 purchase totals =	$1,087.03		$1,192.3264	$1,192.33	$1,192.40	$1,192.30