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	$229.74	8.223%	$248.6315	$248.63	$248.65	$248.60
Purchase #2	$71.95	9.517%	$78.7975	$78.80	$78.80	$78.80
Purchase #3	$154.56	6.405%	$164.4596	$164.46	$164.45	$164.50
Purchase #4	$227.72	3.551%	$235.8063	$235.81	$235.80	$235.80
Purchase #5	$33.46	3.520%	$34.6378	$34.64	$34.65	$34.60
Purchase #6	$185.44	12.667%	$208.9297	$208.93	$208.95	$208.90
Purchase #7	$179.85	10.276%	$198.3314	$198.33	$198.35	$198.30
7 purchase totals =	$1,082.72		$1,169.5938	$1,169.60	$1,169.65	$1,169.50