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	$235.57	5.103%	$247.5911	$247.59	$247.60	$247.60
Purchase #2	$55.98	9.564%	$61.3339	$61.33	$61.35	$61.30
Purchase #3	$80.52	6.291%	$85.5855	$85.59	$85.60	$85.60
Purchase #4	$29.87	12.278%	$33.5374	$33.54	$33.55	$33.50
Purchase #5	$197.84	6.673%	$211.0419	$211.04	$211.05	$211.00
Purchase #6	$201.85	7.738%	$217.4692	$217.47	$217.45	$217.50
Purchase #7	$142.61	7.257%	$152.9592	$152.96	$152.95	$153.00
7 purchase totals =	$944.24		$1,009.5182	$1,009.52	$1,009.55	$1,009.50