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	$193.82	7.334%	$208.0348	$208.03	$208.05	$208.00
Purchase #2	$129.42	5.426%	$136.4423	$136.44	$136.45	$136.40
Purchase #3	$99.32	13.351%	$112.5802	$112.58	$112.60	$112.60
Purchase #4	$145.64	11.297%	$162.093	$162.09	$162.10	$162.10
Purchase #5	$101.60	11.103%	$112.8806	$112.88	$112.90	$112.90
Purchase #6	$213.38	12.615%	$240.2979	$240.30	$240.30	$240.30
Purchase #7	$35.67	12.498%	$40.128	$40.13	$40.15	$40.10
7 purchase totals =	$918.85		$1,012.4568	$1,012.45	$1,012.55	$1,012.40