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	$234.54	12.568%	$264.017	$264.02	$264.00	$264.00
Purchase #2	$51.60	11.741%	$57.6584	$57.66	$57.65	$57.70
Purchase #3	$173.55	7.134%	$185.9311	$185.93	$185.95	$185.90
Purchase #4	$164.52	10.579%	$181.9246	$181.92	$181.90	$181.90
Purchase #5	$70.91	4.463%	$74.0747	$74.07	$74.05	$74.10
Purchase #6	$200.89	5.798%	$212.5376	$212.54	$212.55	$212.50
Purchase #7	$182.47	12.550%	$205.37	$205.37	$205.35	$205.40
7 purchase totals =	$1,078.48		$1,181.5134	$1,181.51	$1,181.45	$1,181.50