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	$228.72	9.708%	$250.9241	$250.92	$250.90	$250.90
Purchase #2	$90.99	10.371%	$100.4266	$100.43	$100.45	$100.40
Purchase #3	$139.38	8.730%	$151.5479	$151.55	$151.55	$151.50
Purchase #4	$78.68	12.632%	$88.6189	$88.62	$88.60	$88.60
Purchase #5	$197.81	6.818%	$211.2967	$211.30	$211.30	$211.30
Purchase #6	$107.79	4.427%	$112.5619	$112.56	$112.55	$112.60
Purchase #7	$89.25	13.184%	$101.0167	$101.02	$101.00	$101.00
7 purchase totals =	$932.62		$1,016.3928	$1,016.40	$1,016.35	$1,016.30