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	$89.82	13.521%	$101.9646	$101.96	$101.95	$102.00
Purchase #2	$176.76	5.789%	$186.9926	$186.99	$187.00	$187.00
Purchase #3	$37.42	13.560%	$42.4942	$42.49	$42.50	$42.50
Purchase #4	$72.47	5.668%	$76.5776	$76.58	$76.60	$76.60
Purchase #5	$113.73	8.592%	$123.5017	$123.50	$123.50	$123.50
Purchase #6	$131.78	8.521%	$143.009	$143.01	$143.00	$143.00
Purchase #7	$214.56	5.395%	$226.1355	$226.14	$226.15	$226.10
7 purchase totals =	$836.54		$900.6752	$900.67	$900.70	$900.70