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	$117.61	13.854%	$133.9037	$133.90	$133.90	$133.90
Purchase #2	$53.70	13.654%	$61.0322	$61.03	$61.05	$61.00
Purchase #3	$109.71	7.848%	$118.32	$118.32	$118.30	$118.30
Purchase #4	$185.61	12.418%	$208.659	$208.66	$208.65	$208.70
Purchase #5	$248.26	12.485%	$279.2553	$279.26	$279.25	$279.30
Purchase #6	$116.99	13.569%	$132.8644	$132.86	$132.85	$132.90
Purchase #7	$84.66	5.306%	$89.1521	$89.15	$89.15	$89.20
7 purchase totals =	$916.54		$1,023.1867	$1,023.18	$1,023.15	$1,023.30