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	$134.49	11.110%	$149.4318	$149.43	$149.45	$149.40
Purchase #2	$90.41	12.372%	$101.5955	$101.60	$101.60	$101.60
Purchase #3	$178.68	4.393%	$186.5294	$186.53	$186.55	$186.50
Purchase #4	$240.30	7.582%	$258.5195	$258.52	$258.50	$258.50
Purchase #5	$73.61	13.420%	$83.4885	$83.49	$83.50	$83.50
Purchase #6	$118.55	7.719%	$127.7009	$127.70	$127.70	$127.70
Purchase #7	$180.53	6.873%	$192.9378	$192.94	$192.95	$192.90
7 purchase totals =	$1,016.57		$1,100.2034	$1,100.21	$1,100.25	$1,100.10