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	$228.69	13.647%	$259.8993	$259.90	$259.90	$259.90
Purchase #2	$229.48	11.520%	$255.9161	$255.92	$255.90	$255.90
Purchase #3	$200.34	5.795%	$211.9497	$211.95	$211.95	$211.90
Purchase #4	$119.97	6.629%	$127.9228	$127.92	$127.90	$127.90
Purchase #5	$162.40	11.390%	$180.8974	$180.90	$180.90	$180.90
Purchase #6	$184.86	3.141%	$190.6665	$190.67	$190.65	$190.70
Purchase #7	$151.40	3.523%	$156.7338	$156.73	$156.75	$156.70
7 purchase totals =	$1,277.14		$1,383.9856	$1,383.99	$1,383.95	$1,383.90