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	$225.63	8.368%	$244.5107	$244.51	$244.50	$244.50
Purchase #2	$248.26	5.223%	$261.2266	$261.23	$261.25	$261.20
Purchase #3	$196.55	4.798%	$205.9805	$205.98	$206.00	$206.00
Purchase #4	$94.56	9.305%	$103.3588	$103.36	$103.35	$103.40
Purchase #5	$75.44	9.795%	$82.8293	$82.83	$82.85	$82.80
Purchase #6	$39.94	8.456%	$43.3173	$43.32	$43.30	$43.30
Purchase #7	$139.31	13.374%	$157.9413	$157.94	$157.95	$157.90
7 purchase totals =	$1,019.69		$1,099.1645	$1,099.17	$1,099.20	$1,099.10