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	$208.53	7.195%	$223.5337	$223.53	$223.55	$223.50
Purchase #2	$182.92	12.449%	$205.6917	$205.69	$205.70	$205.70
Purchase #3	$238.50	4.392%	$248.9749	$248.97	$248.95	$249.00
Purchase #4	$71.38	10.323%	$78.7486	$78.75	$78.75	$78.70
Purchase #5	$75.69	12.704%	$85.3057	$85.31	$85.30	$85.30
Purchase #6	$88.99	5.874%	$94.2173	$94.22	$94.20	$94.20
Purchase #7	$127.82	6.499%	$136.127	$136.13	$136.15	$136.10
7 purchase totals =	$993.83		$1,072.5989	$1,072.60	$1,072.60	$1,072.50