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	$134.98	5.638%	$142.5902	$142.59	$142.60	$142.60
Purchase #2	$138.94	9.735%	$152.4658	$152.47	$152.45	$152.50
Purchase #3	$101.38	11.858%	$113.4016	$113.40	$113.40	$113.40
Purchase #4	$15.98	12.666%	$18.004	$18.00	$18.00	$18.00
Purchase #5	$189.48	4.555%	$198.1108	$198.11	$198.10	$198.10
Purchase #6	$168.71	4.857%	$176.9042	$176.90	$176.90	$176.90
Purchase #7	$198.31	11.467%	$221.0502	$221.05	$221.05	$221.10
7 purchase totals =	$947.78		$1,022.5268	$1,022.52	$1,022.50	$1,022.60