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	$142.37	8.767%	$154.8516	$154.85	$154.85	$154.90
Purchase #2	$196.97	8.846%	$214.394	$214.39	$214.40	$214.40
Purchase #3	$111.46	6.824%	$119.066	$119.07	$119.05	$119.10
Purchase #4	$227.39	4.736%	$238.1592	$238.16	$238.15	$238.20
Purchase #5	$41.65	3.674%	$43.1802	$43.18	$43.20	$43.20
Purchase #6	$80.28	12.732%	$90.5012	$90.50	$90.50	$90.50
Purchase #7	$89.27	7.633%	$96.084	$96.08	$96.10	$96.10
7 purchase totals =	$889.39		$956.2362	$956.23	$956.25	$956.40