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	$131.59	9.276%	$143.7963	$143.80	$143.80	$143.80
Purchase #2	$65.72	10.842%	$72.8454	$72.85	$72.85	$72.80
Purchase #3	$221.72	3.839%	$230.2318	$230.23	$230.25	$230.20
Purchase #4	$106.69	9.445%	$116.7669	$116.77	$116.75	$116.80
Purchase #5	$150.34	10.725%	$166.464	$166.46	$166.45	$166.50
Purchase #6	$248.32	4.648%	$259.8619	$259.86	$259.85	$259.90
Purchase #7	$240.39	12.790%	$271.1359	$271.14	$271.15	$271.10
7 purchase totals =	$1,164.77		$1,261.1022	$1,261.11	$1,261.10	$1,261.10