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	$44.85	10.522%	$49.5691	$49.57	$49.55	$49.60
Purchase #2	$180.49	11.320%	$200.9215	$200.92	$200.90	$200.90
Purchase #3	$65.43	11.607%	$73.0245	$73.02	$73.00	$73.00
Purchase #4	$23.56	7.671%	$25.3673	$25.37	$25.35	$25.40
Purchase #5	$242.40	8.678%	$263.4355	$263.44	$263.45	$263.40
Purchase #6	$243.25	8.280%	$263.3911	$263.39	$263.40	$263.40
Purchase #7	$215.87	4.169%	$224.8696	$224.87	$224.85	$224.90
7 purchase totals =	$1,015.85		$1,100.5786	$1,100.58	$1,100.50	$1,100.60