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	$14.32	8.796%	$15.5796	$15.58	$15.60	$15.60
Purchase #2	$27.59	5.605%	$29.1364	$29.14	$29.15	$29.10
Purchase #3	$101.79	9.355%	$111.3125	$111.31	$111.30	$111.30
Purchase #4	$212.32	11.424%	$236.5754	$236.58	$236.60	$236.60
Purchase #5	$189.64	10.184%	$208.9529	$208.95	$208.95	$209.00
Purchase #6	$202.37	10.302%	$223.2182	$223.22	$223.20	$223.20
Purchase #7	$178.66	7.781%	$192.5615	$192.56	$192.55	$192.60
7 purchase totals =	$926.69		$1,017.3365	$1,017.34	$1,017.35	$1,017.40