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	$181.32	12.556%	$204.0865	$204.09	$204.10	$204.10
Purchase #2	$241.85	5.387%	$254.8785	$254.88	$254.90	$254.90
Purchase #3	$115.57	10.510%	$127.7164	$127.72	$127.70	$127.70
Purchase #4	$248.33	3.373%	$256.7062	$256.71	$256.70	$256.70
Purchase #5	$224.63	4.853%	$235.5313	$235.53	$235.55	$235.50
Purchase #6	$62.68	7.335%	$67.2776	$67.28	$67.30	$67.30
Purchase #7	$168.45	11.552%	$187.9093	$187.91	$187.90	$187.90
7 purchase totals =	$1,242.83		$1,334.1058	$1,334.12	$1,334.15	$1,334.10