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	$132.86	7.776%	$143.1912	$143.19	$143.20	$143.20
Purchase #2	$84.64	13.306%	$95.9022	$95.90	$95.90	$95.90
Purchase #3	$89.45	7.685%	$96.3242	$96.32	$96.30	$96.30
Purchase #4	$105.89	13.583%	$120.273	$120.27	$120.25	$120.30
Purchase #5	$105.53	3.523%	$109.2478	$109.25	$109.25	$109.20
Purchase #6	$161.28	13.207%	$182.5802	$182.58	$182.60	$182.60
Purchase #7	$43.55	11.226%	$48.4389	$48.44	$48.45	$48.40
7 purchase totals =	$723.20		$795.9575	$795.95	$795.95	$795.90