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	$181.38	10.389%	$200.2236	$200.22	$200.20	$200.20
Purchase #2	$53.97	3.367%	$55.7872	$55.79	$55.80	$55.80
Purchase #3	$57.34	3.438%	$59.3113	$59.31	$59.30	$59.30
Purchase #4	$35.58	6.484%	$37.887	$37.89	$37.90	$37.90
Purchase #5	$142.93	9.814%	$156.9572	$156.96	$156.95	$157.00
Purchase #6	$179.26	12.380%	$201.4524	$201.45	$201.45	$201.50
Purchase #7	$211.45	4.873%	$221.754	$221.75	$221.75	$221.80
7 purchase totals =	$861.91		$933.3727	$933.37	$933.35	$933.50