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	$174.43	11.448%	$194.3987	$194.40	$194.40	$194.40
Purchase #2	$87.35	7.698%	$94.0742	$94.07	$94.05	$94.10
Purchase #3	$195.71	4.848%	$205.198	$205.20	$205.20	$205.20
Purchase #4	$92.94	12.864%	$104.8958	$104.90	$104.90	$104.90
Purchase #5	$164.82	3.778%	$171.0469	$171.05	$171.05	$171.00
Purchase #6	$225.44	9.829%	$247.5985	$247.60	$247.60	$247.60
Purchase #7	$77.69	7.366%	$83.4126	$83.41	$83.40	$83.40
7 purchase totals =	$1,018.38		$1,100.6247	$1,100.63	$1,100.60	$1,100.60