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	$200.65	10.712%	$222.1436	$222.14	$222.15	$222.10
Purchase #2	$83.75	6.734%	$89.3897	$89.39	$89.40	$89.40
Purchase #3	$51.41	7.522%	$55.2771	$55.28	$55.30	$55.30
Purchase #4	$246.92	5.592%	$260.7278	$260.73	$260.75	$260.70
Purchase #5	$143.61	9.807%	$157.6938	$157.69	$157.70	$157.70
Purchase #6	$224.56	3.788%	$233.0663	$233.07	$233.05	$233.10
Purchase #7	$200.96	13.720%	$228.5317	$228.53	$228.55	$228.50
7 purchase totals =	$1,151.86		$1,246.8300	$1,246.83	$1,246.90	$1,246.80