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	$135.47	7.397%	$145.4907	$145.49	$145.50	$145.50
Purchase #2	$186.97	5.254%	$196.7934	$196.79	$196.80	$196.80
Purchase #3	$135.80	12.362%	$152.5876	$152.59	$152.60	$152.60
Purchase #4	$201.86	11.107%	$224.2806	$224.28	$224.30	$224.30
Purchase #5	$111.67	7.686%	$120.253	$120.25	$120.25	$120.30
Purchase #6	$138.63	10.469%	$153.1432	$153.14	$153.15	$153.10
Purchase #7	$14.78	4.314%	$15.4176	$15.42	$15.40	$15.40
7 purchase totals =	$925.18		$1,007.9661	$1,007.96	$1,008.00	$1,008.00