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	$138.88	9.409%	$151.9472	$151.95	$151.95	$151.90
Purchase #2	$54.69	11.775%	$61.1297	$61.13	$61.15	$61.10
Purchase #3	$102.32	8.570%	$111.0888	$111.09	$111.10	$111.10
Purchase #4	$72.85	9.736%	$79.9427	$79.94	$79.95	$79.90
Purchase #5	$54.45	12.534%	$61.2748	$61.27	$61.25	$61.30
Purchase #6	$168.39	8.365%	$182.4758	$182.48	$182.50	$182.50
Purchase #7	$139.65	8.486%	$151.5007	$151.50	$151.50	$151.50
7 purchase totals =	$731.23		$799.3597	$799.36	$799.40	$799.30