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	$104.44	11.608%	$116.5634	$116.56	$116.55	$116.60
Purchase #2	$141.33	7.810%	$152.3679	$152.37	$152.35	$152.40
Purchase #3	$97.60	3.517%	$101.0326	$101.03	$101.05	$101.00
Purchase #4	$231.60	4.133%	$241.172	$241.17	$241.15	$241.20
Purchase #5	$113.71	3.429%	$117.6091	$117.61	$117.60	$117.60
Purchase #6	$220.79	9.533%	$241.8379	$241.84	$241.85	$241.80
Purchase #7	$105.43	13.768%	$119.9456	$119.95	$119.95	$119.90
7 purchase totals =	$1,014.90		$1,090.5285	$1,090.53	$1,090.50	$1,090.50