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	$105.37	6.647%	$112.3739	$112.37	$112.35	$112.40
Purchase #2	$34.47	3.548%	$35.693	$35.69	$35.70	$35.70
Purchase #3	$240.59	8.193%	$260.3015	$260.30	$260.30	$260.30
Purchase #4	$101.90	9.292%	$111.3685	$111.37	$111.35	$111.40
Purchase #5	$202.54	13.409%	$229.6986	$229.70	$229.70	$229.70
Purchase #6	$170.94	8.173%	$184.9109	$184.91	$184.90	$184.90
Purchase #7	$111.66	10.649%	$123.5507	$123.55	$123.55	$123.60
7 purchase totals =	$967.47		$1,057.8971	$1,057.89	$1,057.85	$1,058.00