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	$118.35	3.401%	$122.3751	$122.38	$122.40	$122.40
Purchase #2	$186.93	13.427%	$212.0291	$212.03	$212.05	$212.00
Purchase #3	$61.34	5.494%	$64.71	$64.71	$64.70	$64.70
Purchase #4	$105.55	5.262%	$111.104	$111.10	$111.10	$111.10
Purchase #5	$63.80	3.661%	$66.1357	$66.14	$66.15	$66.10
Purchase #6	$66.92	4.798%	$70.1308	$70.13	$70.15	$70.10
Purchase #7	$120.40	5.795%	$127.3772	$127.38	$127.40	$127.40
7 purchase totals =	$723.29		$773.8619	$773.87	$773.95	$773.80