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	$103.51	9.142%	$112.9729	$112.97	$112.95	$113.00
Purchase #2	$230.49	12.189%	$258.5844	$258.58	$258.60	$258.60
Purchase #3	$199.84	11.400%	$222.6218	$222.62	$222.60	$222.60
Purchase #4	$156.62	8.384%	$169.751	$169.75	$169.75	$169.80
Purchase #5	$62.78	3.499%	$64.9767	$64.98	$65.00	$65.00
Purchase #6	$93.28	5.108%	$98.0447	$98.04	$98.05	$98.00
Purchase #7	$184.37	6.383%	$196.1383	$196.14	$196.15	$196.10
7 purchase totals =	$1,030.89		$1,123.0898	$1,123.08	$1,123.10	$1,123.10