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	$40.28	4.383%	$42.0455	$42.05	$42.05	$42.00
Purchase #2	$248.92	10.249%	$274.4318	$274.43	$274.45	$274.40
Purchase #3	$223.45	3.273%	$230.7635	$230.76	$230.75	$230.80
Purchase #4	$72.43	5.739%	$76.5868	$76.59	$76.60	$76.60
Purchase #5	$133.72	7.838%	$144.201	$144.20	$144.20	$144.20
Purchase #6	$148.88	7.488%	$160.0281	$160.03	$160.05	$160.00
Purchase #7	$173.86	6.599%	$185.333	$185.33	$185.35	$185.30
7 purchase totals =	$1,041.54		$1,113.3897	$1,113.39	$1,113.45	$1,113.30