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	$181.56	10.460%	$200.5512	$200.55	$200.55	$200.60
Purchase #2	$89.32	12.594%	$100.569	$100.57	$100.55	$100.60
Purchase #3	$22.72	3.370%	$23.4857	$23.49	$23.50	$23.50
Purchase #4	$65.96	9.724%	$72.374	$72.37	$72.35	$72.40
Purchase #5	$42.44	9.346%	$46.4064	$46.41	$46.40	$46.40
Purchase #6	$241.49	9.454%	$264.3205	$264.32	$264.30	$264.30
Purchase #7	$192.96	11.308%	$214.7799	$214.78	$214.80	$214.80
7 purchase totals =	$836.45		$922.4867	$922.49	$922.45	$922.60