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	$224.45	10.830%	$248.7579	$248.76	$248.75	$248.80
Purchase #2	$154.82	12.396%	$174.0115	$174.01	$174.00	$174.00
Purchase #3	$27.95	3.368%	$28.8914	$28.89	$28.90	$28.90
Purchase #4	$182.96	7.548%	$196.7698	$196.77	$196.75	$196.80
Purchase #5	$64.36	4.508%	$67.2613	$67.26	$67.25	$67.30
Purchase #6	$129.91	11.873%	$145.3342	$145.33	$145.35	$145.30
Purchase #7	$226.49	13.639%	$257.381	$257.38	$257.40	$257.40
7 purchase totals =	$1,010.94		$1,118.4071	$1,118.40	$1,118.40	$1,118.50