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	$242.89	13.209%	$274.9733	$274.97	$274.95	$275.00
Purchase #2	$111.86	3.339%	$115.595	$115.60	$115.60	$115.60
Purchase #3	$135.68	10.750%	$150.2656	$150.27	$150.25	$150.30
Purchase #4	$97.94	6.701%	$104.503	$104.50	$104.50	$104.50
Purchase #5	$250.93	3.300%	$259.2107	$259.21	$259.20	$259.20
Purchase #6	$151.61	3.554%	$156.9982	$157.00	$157.00	$157.00
Purchase #7	$61.42	7.325%	$65.919	$65.92	$65.90	$65.90
7 purchase totals =	$1,052.33		$1,127.4648	$1,127.47	$1,127.40	$1,127.50