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	$33.31	9.707%	$36.5434	$36.54	$36.55	$36.50
Purchase #2	$194.79	8.511%	$211.3686	$211.37	$211.35	$211.40
Purchase #3	$179.37	3.471%	$185.5959	$185.60	$185.60	$185.60
Purchase #4	$167.63	8.531%	$181.9305	$181.93	$181.95	$181.90
Purchase #5	$240.25	7.611%	$258.5354	$258.54	$258.55	$258.50
Purchase #6	$156.93	6.355%	$166.9029	$166.90	$166.90	$166.90
Purchase #7	$127.89	8.111%	$138.2632	$138.26	$138.25	$138.30
7 purchase totals =	$1,100.17		$1,179.1399	$1,179.14	$1,179.15	$1,179.10