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	$13.85	4.844%	$14.5209	$14.52	$14.50	$14.50
Purchase #2	$249.87	12.619%	$281.4011	$281.40	$281.40	$281.40
Purchase #3	$230.25	3.335%	$237.9288	$237.93	$237.95	$237.90
Purchase #4	$146.79	6.870%	$156.8745	$156.87	$156.85	$156.90
Purchase #5	$183.49	12.512%	$206.4483	$206.45	$206.45	$206.40
Purchase #6	$61.31	9.441%	$67.0983	$67.10	$67.10	$67.10
Purchase #7	$37.29	3.647%	$38.65	$38.65	$38.65	$38.70
7 purchase totals =	$922.85		$1,002.9219	$1,002.92	$1,002.90	$1,002.90