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	$83.89	5.630%	$88.613	$88.61	$88.60	$88.60
Purchase #2	$63.75	13.712%	$72.4914	$72.49	$72.50	$72.50
Purchase #3	$192.41	9.770%	$211.2085	$211.21	$211.20	$211.20
Purchase #4	$148.43	10.825%	$164.4975	$164.50	$164.50	$164.50
Purchase #5	$68.70	13.603%	$78.0453	$78.05	$78.05	$78.00
Purchase #6	$118.49	9.678%	$129.9575	$129.96	$129.95	$130.00
Purchase #7	$174.40	12.813%	$196.7459	$196.75	$196.75	$196.70
7 purchase totals =	$850.07		$941.5591	$941.57	$941.55	$941.50