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	$101.89	9.788%	$111.863	$111.86	$111.85	$111.90
Purchase #2	$186.35	4.551%	$194.8308	$194.83	$194.85	$194.80
Purchase #3	$180.92	7.675%	$194.8056	$194.81	$194.80	$194.80
Purchase #4	$141.83	4.251%	$147.8592	$147.86	$147.85	$147.90
Purchase #5	$206.60	5.124%	$217.1862	$217.19	$217.20	$217.20
Purchase #6	$7.69	12.806%	$8.6748	$8.67	$8.65	$8.70
Purchase #7	$185.47	12.240%	$208.1715	$208.17	$208.15	$208.20
7 purchase totals =	$1,010.75		$1,083.3911	$1,083.39	$1,083.35	$1,083.50