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	$149.50	8.575%	$162.3196	$162.32	$162.30	$162.30
Purchase #2	$155.99	7.113%	$167.0856	$167.09	$167.10	$167.10
Purchase #3	$186.33	8.144%	$201.5047	$201.50	$201.50	$201.50
Purchase #4	$142.25	10.520%	$157.2147	$157.21	$157.20	$157.20
Purchase #5	$146.92	3.400%	$151.9153	$151.92	$151.90	$151.90
Purchase #6	$78.59	13.856%	$89.4794	$89.48	$89.50	$89.50
Purchase #7	$54.39	6.577%	$57.9672	$57.97	$57.95	$58.00
7 purchase totals =	$913.97		$987.4865	$987.49	$987.45	$987.50