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	$155.89	12.512%	$175.395	$175.40	$175.40	$175.40
Purchase #2	$14.51	6.787%	$15.4948	$15.49	$15.50	$15.50
Purchase #3	$98.33	6.273%	$104.4982	$104.50	$104.50	$104.50
Purchase #4	$88.76	13.202%	$100.4781	$100.48	$100.50	$100.50
Purchase #5	$28.39	12.762%	$32.0131	$32.01	$32.00	$32.00
Purchase #6	$235.54	11.447%	$262.5023	$262.50	$262.50	$262.50
Purchase #7	$211.89	6.300%	$225.2391	$225.24	$225.25	$225.20
7 purchase totals =	$833.31		$915.6206	$915.62	$915.65	$915.60