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	$166.85	3.529%	$172.7381	$172.74	$172.75	$172.70
Purchase #2	$106.66	9.264%	$116.541	$116.54	$116.55	$116.50
Purchase #3	$137.89	4.649%	$144.3005	$144.30	$144.30	$144.30
Purchase #4	$103.86	5.388%	$109.456	$109.46	$109.45	$109.50
Purchase #5	$210.27	7.593%	$226.2358	$226.24	$226.25	$226.20
Purchase #6	$180.39	4.462%	$188.439	$188.44	$188.45	$188.40
Purchase #7	$41.49	8.343%	$44.9515	$44.95	$44.95	$45.00
7 purchase totals =	$947.41		$1,002.6619	$1,002.67	$1,002.70	$1,002.60