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	$154.70	4.779%	$162.0931	$162.09	$162.10	$162.10
Purchase #2	$119.68	6.846%	$127.8733	$127.87	$127.85	$127.90
Purchase #3	$186.66	7.653%	$200.9451	$200.95	$200.95	$200.90
Purchase #4	$148.69	8.207%	$160.893	$160.89	$160.90	$160.90
Purchase #5	$247.98	13.182%	$280.6687	$280.67	$280.65	$280.70
Purchase #6	$165.39	3.824%	$171.7145	$171.71	$171.70	$171.70
Purchase #7	$249.58	13.742%	$283.8773	$283.88	$283.90	$283.90
7 purchase totals =	$1,272.68		$1,388.0650	$1,388.06	$1,388.05	$1,388.10