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	$127.90	12.263%	$143.5844	$143.58	$143.60	$143.60
Purchase #2	$92.61	5.792%	$97.974	$97.97	$97.95	$98.00
Purchase #3	$86.50	11.346%	$96.3143	$96.31	$96.30	$96.30
Purchase #4	$57.59	13.823%	$65.5507	$65.55	$65.55	$65.60
Purchase #5	$110.60	11.469%	$123.2847	$123.28	$123.30	$123.30
Purchase #6	$35.35	7.736%	$38.0847	$38.08	$38.10	$38.10
Purchase #7	$143.65	6.858%	$153.5015	$153.50	$153.50	$153.50
7 purchase totals =	$654.20		$718.2943	$718.27	$718.30	$718.40