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	$167.48	9.194%	$182.8781	$182.88	$182.90	$182.90
Purchase #2	$225.46	7.487%	$242.3402	$242.34	$242.35	$242.30
Purchase #3	$70.30	11.683%	$78.5131	$78.51	$78.50	$78.50
Purchase #4	$231.33	13.686%	$262.9898	$262.99	$263.00	$263.00
Purchase #5	$115.58	3.673%	$119.8253	$119.83	$119.85	$119.80
Purchase #6	$17.31	12.357%	$19.449	$19.45	$19.45	$19.40
Purchase #7	$159.37	9.537%	$174.5691	$174.57	$174.55	$174.60
7 purchase totals =	$986.83		$1,080.5646	$1,080.57	$1,080.60	$1,080.50