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	$39.84	4.589%	$41.6683	$41.67	$41.65	$41.70
Purchase #2	$197.34	9.525%	$216.1366	$216.14	$216.15	$216.10
Purchase #3	$86.28	5.229%	$90.7916	$90.79	$90.80	$90.80
Purchase #4	$220.27	10.815%	$244.0922	$244.09	$244.10	$244.10
Purchase #5	$104.63	11.664%	$116.834	$116.83	$116.85	$116.80
Purchase #6	$154.29	9.265%	$168.585	$168.59	$168.60	$168.60
Purchase #7	$161.90	3.387%	$167.3836	$167.38	$167.40	$167.40
7 purchase totals =	$964.55		$1,045.4913	$1,045.49	$1,045.55	$1,045.50