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	$96.86	4.705%	$101.4173	$101.42	$101.40	$101.40
Purchase #2	$145.68	7.106%	$156.032	$156.03	$156.05	$156.00
Purchase #3	$133.83	13.164%	$151.4474	$151.45	$151.45	$151.40
Purchase #4	$44.88	3.683%	$46.5329	$46.53	$46.55	$46.50
Purchase #5	$92.36	7.770%	$99.5364	$99.54	$99.55	$99.50
Purchase #6	$175.91	3.752%	$182.5101	$182.51	$182.50	$182.50
Purchase #7	$218.55	3.406%	$225.9938	$225.99	$226.00	$226.00
7 purchase totals =	$908.07		$963.4699	$963.47	$963.50	$963.30