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	$92.97	10.276%	$102.5236	$102.52	$102.50	$102.50
Purchase #2	$163.90	11.381%	$182.5535	$182.55	$182.55	$182.60
Purchase #3	$57.67	8.431%	$62.5322	$62.53	$62.55	$62.50
Purchase #4	$172.42	12.717%	$194.3467	$194.35	$194.35	$194.30
Purchase #5	$87.37	13.476%	$99.144	$99.14	$99.15	$99.10
Purchase #6	$168.64	10.720%	$186.7182	$186.72	$186.70	$186.70
Purchase #7	$240.52	6.152%	$255.3168	$255.32	$255.30	$255.30
7 purchase totals =	$983.49		$1,083.1350	$1,083.13	$1,083.10	$1,083.00