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	$56.78	9.328%	$62.0764	$62.08	$62.10	$62.10
Purchase #2	$150.60	4.173%	$156.8845	$156.88	$156.90	$156.90
Purchase #3	$88.43	9.507%	$96.837	$96.84	$96.85	$96.80
Purchase #4	$240.83	13.219%	$272.6653	$272.67	$272.65	$272.70
Purchase #5	$14.92	9.650%	$16.3598	$16.36	$16.35	$16.40
Purchase #6	$202.90	12.363%	$227.9845	$227.98	$228.00	$228.00
Purchase #7	$164.55	12.816%	$185.6387	$185.64	$185.65	$185.60
7 purchase totals =	$919.01		$1,018.4462	$1,018.45	$1,018.50	$1,018.50