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	$167.48	12.422%	$188.2844	$188.28	$188.30	$188.30
Purchase #2	$32.42	6.427%	$34.5036	$34.50	$34.50	$34.50
Purchase #3	$61.88	3.566%	$64.0866	$64.09	$64.10	$64.10
Purchase #4	$52.25	6.247%	$55.5141	$55.51	$55.50	$55.50
Purchase #5	$236.41	9.102%	$257.928	$257.93	$257.95	$257.90
Purchase #6	$51.56	5.710%	$54.5041	$54.50	$54.50	$54.50
Purchase #7	$40.86	13.807%	$46.5015	$46.50	$46.50	$46.50
7 purchase totals =	$642.86		$701.3223	$701.31	$701.35	$701.30