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	$62.91	3.575%	$65.159	$65.16	$65.15	$65.20
Purchase #2	$78.34	3.610%	$81.1681	$81.17	$81.15	$81.20
Purchase #3	$131.39	4.739%	$137.6166	$137.62	$137.60	$137.60
Purchase #4	$72.42	13.538%	$82.2242	$82.22	$82.20	$82.20
Purchase #5	$115.90	7.588%	$124.6945	$124.69	$124.70	$124.70
Purchase #6	$197.60	7.445%	$212.3113	$212.31	$212.30	$212.30
Purchase #7	$176.96	4.371%	$184.6949	$184.69	$184.70	$184.70
7 purchase totals =	$835.52		$887.8686	$887.86	$887.80	$887.90