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	$11.31	4.360%	$11.8031	$11.80	$11.80	$11.80
Purchase #2	$176.35	11.206%	$196.1118	$196.11	$196.10	$196.10
Purchase #3	$5.33	3.523%	$5.5178	$5.52	$5.50	$5.50
Purchase #4	$200.50	4.443%	$209.4082	$209.41	$209.40	$209.40
Purchase #5	$11.49	3.551%	$11.898	$11.90	$11.90	$11.90
Purchase #6	$47.87	3.457%	$49.5249	$49.52	$49.50	$49.50
Purchase #7	$225.60	9.154%	$246.2514	$246.25	$246.25	$246.30
7 purchase totals =	$678.45		$730.5152	$730.51	$730.45	$730.50